I am unable to reproduce the problem in devstack. Can you please let me know how to reproduce the problem?

vagrant@devstack:~$ source devstack/openrc 
WARNING: setting legacy OS_TENANT_NAME to support cli tools.
vagrant@devstack:~$ openstack ec2 credentials create
+------------+------------------------------------------------------------------------------------------------------------------------------------------+
| Field      | Value                                                                                                                                    |
+------------+------------------------------------------------------------------------------------------------------------------------------------------+
| access     | d58750aab57546b8838bfb072ca9f39b                                                                                                         |
| links      | {u'self': u'http://192.168.1.20/identity/v3/users/aaf1da0b2dee4a89be8350533d40628b/credentials/OS-EC2/d58750aab57546b8838bfb072ca9f39b'} |
| project_id | 5f5b5ca4fffe4a90b15149c4e9b12222                                                                                                         |
| secret     | 1a6895b1d1f549a693795d93f41aef90                                                                                                         |
| trust_id   | None                                                                                                                                     |
| user_id    | aaf1da0b2dee4a89be8350533d40628b                                                                                                         |
+------------+------------------------------------------------------------------------------------------------------------------------------------------+
vagrant@devstack:~$ openstack ec2 credentials create
+------------+------------------------------------------------------------------------------------------------------------------------------------------+
| Field      | Value                                                                                                                                    |
+------------+------------------------------------------------------------------------------------------------------------------------------------------+
| access     | 7f003b5f4b7945c8aa6db512021111ab                                                                                                         |
| links      | {u'self': u'http://192.168.1.20/identity/v3/users/aaf1da0b2dee4a89be8350533d40628b/credentials/OS-EC2/7f003b5f4b7945c8aa6db512021111ab'} |
| project_id | 5f5b5ca4fffe4a90b15149c4e9b12222                                                                                                         |
| secret     | ad22cbc8d02744f4b38d65ab1f17ef0e                                                                                                         |
| trust_id   | None                                                                                                                                     |
| user_id    | aaf1da0b2dee4a89be8350533d40628b                                                                                                         |
+------------+------------------------------------------------------------------------------------------------------------------------------------------+
vagrant@devstack:~$ openstack ec2 credentials list
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| Access                           | Secret                           | Project ID                       | User ID                          |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| d58750aab57546b8838bfb072ca9f39b | 1a6895b1d1f549a693795d93f41aef90 | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
| 7f003b5f4b7945c8aa6db512021111ab | ad22cbc8d02744f4b38d65ab1f17ef0e | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
vagrant@devstack:~$ openstack ec2 credentials list
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| Access                           | Secret                           | Project ID                       | User ID                          |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| d58750aab57546b8838bfb072ca9f39b | 1a6895b1d1f549a693795d93f41aef90 | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
| 7f003b5f4b7945c8aa6db512021111ab | ad22cbc8d02744f4b38d65ab1f17ef0e | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
vagrant@devstack:~$ openstack ec2 credentials list
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| Access                           | Secret                           | Project ID                       | User ID                          |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| d58750aab57546b8838bfb072ca9f39b | 1a6895b1d1f549a693795d93f41aef90 | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
| 7f003b5f4b7945c8aa6db512021111ab | ad22cbc8d02744f4b38d65ab1f17ef0e | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
vagrant@devstack:~$ openstack ec2 credentials list
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| Access                           | Secret                           | Project ID                       | User ID                          |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| d58750aab57546b8838bfb072ca9f39b | 1a6895b1d1f549a693795d93f41aef90 | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
| 7f003b5f4b7945c8aa6db512021111ab | ad22cbc8d02744f4b38d65ab1f17ef0e | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
vagrant@devstack:~$ openstack ec2 credentials list
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| Access                           | Secret                           | Project ID                       | User ID                          |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| d58750aab57546b8838bfb072ca9f39b | 1a6895b1d1f549a693795d93f41aef90 | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
| 7f003b5f4b7945c8aa6db512021111ab | ad22cbc8d02744f4b38d65ab1f17ef0e | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
vagrant@devstack:~$ source devstack/openrc admin admin
WARNING: setting legacy OS_TENANT_NAME to support cli tools.
vagrant@devstack:~$ openstack ec2 credentials list --user aaf1da0b2dee4a89be8350533d40628b
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| Access                           | Secret                           | Project ID                       | User ID                          |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| d58750aab57546b8838bfb072ca9f39b | 1a6895b1d1f549a693795d93f41aef90 | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
| 7f003b5f4b7945c8aa6db512021111ab | ad22cbc8d02744f4b38d65ab1f17ef0e | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
vagrant@devstack:~$ openstack ec2 credentials list --user aaf1da0b2dee4a89be8350533d40628b
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| Access                           | Secret                           | Project ID                       | User ID                          |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| d58750aab57546b8838bfb072ca9f39b | 1a6895b1d1f549a693795d93f41aef90 | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
| 7f003b5f4b7945c8aa6db512021111ab | ad22cbc8d02744f4b38d65ab1f17ef0e | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
vagrant@devstack:~$ openstack ec2 credentials list --user aaf1da0b2dee4a89be8350533d40628b
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| Access                           | Secret                           | Project ID                       | User ID                          |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| d58750aab57546b8838bfb072ca9f39b | 1a6895b1d1f549a693795d93f41aef90 | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
| 7f003b5f4b7945c8aa6db512021111ab | ad22cbc8d02744f4b38d65ab1f17ef0e | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
vagrant@devstack:~$ openstack ec2 credentials list --user aaf1da0b2dee4a89be8350533d40628b
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| Access                           | Secret                           | Project ID                       | User ID                          |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
| d58750aab57546b8838bfb072ca9f39b | 1a6895b1d1f549a693795d93f41aef90 | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
| 7f003b5f4b7945c8aa6db512021111ab | ad22cbc8d02744f4b38d65ab1f17ef0e | 5f5b5ca4fffe4a90b15149c4e9b12222 | aaf1da0b2dee4a89be8350533d40628b |
+----------------------------------+----------------------------------+----------------------------------+----------------------------------+
vagrant@devstack:~$ grep cache /etc/keystone/keystone.conf 
[cache]
memcache_servers = localhost:11211
backend = dogpile.cache.memcached