By the way here is the state of placement allocations when the bug is present (on master):

$ openstack resource provider list
+--------------------------------------+-----------+------------+--------------------------------------+----------------------+
| uuid                                 | name      | generation | root_provider_uuid                   | parent_provider_uuid |
+--------------------------------------+-----------+------------+--------------------------------------+----------------------+
| 513a47b7-38af-4fa0-9199-3f6d16d600a6 | devstack0 |        108 | 513a47b7-38af-4fa0-9199-3f6d16d600a6 | None                 |
+--------------------------------------+-----------+------------+--------------------------------------+----------------------+
$ openstack resource provider show --allocations 513a47b7-38af-4fa0-9199-3f6d16d600a6
+----------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Field                | Value                                                                                                                                                                                                               |
+----------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| uuid                 | 513a47b7-38af-4fa0-9199-3f6d16d600a6                                                                                                                                                                                |
| name                 | devstack0                                                                                                                                                                                                           |
| generation           | 108                                                                                                                                                                                                                 |
| root_provider_uuid   | 513a47b7-38af-4fa0-9199-3f6d16d600a6                                                                                                                                                                                |
| parent_provider_uuid | None                                                                                                                                                                                                                |
| allocations          | {'29ea91aa-c1eb-4ea6-bf1a-6459b68be55a': {'resources': {'DISK_GB': 1, 'MEMORY_MB': 256, 'PCPU': 1}, 'consumer_generation': 1}, '6bdb6725-8c3e-422d-8c95-1b7459b2f4bd': {'resources': {'DISK_GB': 1, 'MEMORY_MB':    |
|                      | 256, 'PCPU': 1}, 'consumer_generation': 1}}                                                                                                                                                                         |
+----------------------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+