When doing a conditional GET of an object in an EC policy container a 304 response has the wrong etag value - I believe the etag of the EC fragment is returned.
Section 4.1 of https://tools.ietf.org/html/rfc7232 suggests that the same headers should be returned with a 304 as with a 200, which is the behaviour with a replication policy, and leaking an ec fragment etag does not seem appropriate.
To reproduce:
```
swift@anc-vm-11:~/swift$ swift post c -H 'X-Storage-Policy: ec42'
swift@anc-vm-11:~/swift$ swift upload c LICENSE
LICENSE
swift@anc-vm-11:~/swift$ swift stat c LICENSE --debug
DEBUG:keystoneclient.auth.identity.v3.base:Making authentication request to http://localhost:5000/v3/auth/tokens
INFO:requests.packages.urllib3.connectionpool:Starting new HTTP connection (1): localhost
DEBUG:requests.packages.urllib3.connectionpool:"POST /v3/auth/tokens HTTP/1.1" 201 1941
INFO:requests.packages.urllib3.connectionpool:Starting new HTTP connection (1): saio-1.localdomain
DEBUG:requests.packages.urllib3.connectionpool:"HEAD /v1/AUTH_cfb8d9d45212408b90bc0776117aec9e/c/LICENSE HTTP/1.1" 200 0
DEBUG:swiftclient:REQ: curl -i http://saio-1.localdomain:8080/v1/AUTH_cfb8d9d45212408b90bc0776117aec9e/c/LICENSE -I -H "X-Auth-Token: 160d8b41436c4e8a8b3e7c1e9e45eb22"
DEBUG:swiftclient:RESP STATUS: 200 OK
DEBUG:swiftclient:RESP HEADERS: {u'Content-Length': u'11358', u'X-Object-Meta-Mtime': u'1438093626.975645', u'Accept-Ranges': u'bytes', u'Last-Modified': u'Wed, 16 Mar 2016 16:48:57 GMT', u'Etag': u'3b83ef96387f14655fc854ddc3c6bd57', u'X-Timestamp': u'1458146936.25555', u'X-Trans-Id': u'tx06d9f1358f76403ca4d40-0056e98e86', u'Date': u'Wed, 16 Mar 2016 16:49:11 GMT', u'Content-Type': u'application/octet-stream'}
Account: AUTH_cfb8d9d45212408b90bc0776117aec9e
Container: c
Object: LICENSE
Content Type: application/octet-stream
Content Length: 11358
Last Modified: Wed, 16 Mar 2016 16:48:57 GMT
ETag: 3b83ef96387f14655fc854ddc3c6bd57
Meta Mtime: 1438093626.975645
Accept-Ranges: bytes
X-Timestamp: 1458146936.25555
X-Trans-Id: tx06d9f1358f76403ca4d40-0056e98e86
swift@anc-vm-11:~/swift$ curl -i http://saio-1.localdomain:8080/v1/AUTH_cfb8d9d45212408b90bc0776117aec9e/c/LICENSE -H "X-Auth-Token: 160d8b41436c4e8a8b3e7c1e9e45eb22" -H "If-None-Match: 3b83ef96387f14655fc854ddc3c6bd57" -s |grep Etag
Etag: f6b83623d909796a14144a94175f6765
swift@anc-vm-11:~/swift$ curl -i http://saio-1.localdomain:8080/v1/AUTH_cfb8d9d45212408b90bc0776117aec9e/c/LICENSE -H "X-Auth-Token: 160d8b41436c4e8a8b3e7c1e9e45eb22" -H "If-None-Match: will_not_match" -s |grep Etag
Etag: 3b83ef96387f14655fc854ddc3c6bd57
```
Same with replication policy shows same Etag with 200 and 304 responses:
```
swift@anc-vm-11:~/swift$ swift post c_repl -H 'X-Storage-Policy: gold'
swift@anc-vm-11:~/swift$ swift upload c_repl LICENSE
LICENSE
swift@anc-vm-11:~/swift$ swift stat c_repl LICENSE --debug
DEBUG:keystoneclient.auth.identity.v3.base:Making authentication request to http://localhost:5000/v3/auth/tokens
INFO:requests.packages.urllib3.connectionpool:Starting new HTTP connection (1): localhost
DEBUG:requests.packages.urllib3.connectionpool:"POST /v3/auth/tokens HTTP/1.1" 201 1941
INFO:requests.packages.urllib3.connectionpool:Starting new HTTP connection (1): saio-1.localdomain
DEBUG:requests.packages.urllib3.connectionpool:"HEAD /v1/AUTH_cfb8d9d45212408b90bc0776117aec9e/c_repl/LICENSE HTTP/1.1" 200 0
DEBUG:swiftclient:REQ: curl -i http://saio-1.localdomain:8080/v1/AUTH_cfb8d9d45212408b90bc0776117aec9e/c_repl/LICENSE -I -H "X-Auth-Token: f6c390366e2d4eabae3c631a3d9dc72a"
DEBUG:swiftclient:RESP STATUS: 200 OK
DEBUG:swiftclient:RESP HEADERS: {u'Content-Length': u'11358', u'X-Object-Meta-Mtime': u'1438093626.975645', u'Accept-Ranges': u'bytes', u'Last-Modified': u'Wed, 16 Mar 2016 16:51:16 GMT', u'Etag': u'3b83ef96387f14655fc854ddc3c6bd57', u'X-Timestamp': u'1458147075.40759', u'X-Trans-Id': u'txa065f086bca342ba88262-0056e98f0e', u'Date': u'Wed, 16 Mar 2016 16:51:26 GMT', u'Content-Type': u'application/octet-stream'}
Account: AUTH_cfb8d9d45212408b90bc0776117aec9e
Container: c_repl
Object: LICENSE
Content Type: application/octet-stream
Content Length: 11358
Last Modified: Wed, 16 Mar 2016 16:51:16 GMT
ETag: 3b83ef96387f14655fc854ddc3c6bd57
Meta Mtime: 1438093626.975645
Accept-Ranges: bytes
X-Timestamp: 1458147075.40759
X-Trans-Id: txa065f086bca342ba88262-0056e98f0e
swift@anc-vm-11:~/swift$ curl -i http://saio-1.localdomain:8080/v1/AUTH_cfb8d9d45212408b90bc0776117aec9e/c_repl/LICENSE -H "X-Auth-Token: 160d8b41436c4e8a8b3e7c1e9e45eb22" -H "If-None-Match: 3b83ef96387f14655fc854ddc3c6bd57" -s |grep Etag
Etag: 3b83ef96387f14655fc854ddc3c6bd57
swift@anc-vm-11:~/swift$ curl -i http://saio-1.localdomain:8080/v1/AUTH_cfb8d9d45212408b90bc0776117aec9e/c_repl/LICENSE -H "X-Auth-Token: 160d8b41436c4e8a8b3e7c1e9e45eb22" -H "If-None-Match: will_not_match" -s |grep Etag
Etag: 3b83ef96387f14655fc854ddc3c6bd57
```
Fix proposed to branch: master /review. openstack. org/293633
Review: https:/