Bump API version to 2.3

Some changes have landed in Glance's tree during Kilo that require a
minor bump to the API. The following change is probably the one that had
the biggest impact on the current v2.2 API.

- Allow null fields to be returned: Ieaddd8a686cf7361f18cb1ee83b7887cdca22bd6

ApiImpact
DocImpact

Change-Id: I214ae6466ac85876cc9589069913258e80db29b5
Fixes typo: glance exception additional dot

when I try to fix the glanceclient html output, i found the result has
additional dot before the word quota,as follow
Denying attempt to upload image because it exceeds the .quota: The size
of the data 41126400 will exceed the limit. 11210240 bytes remaining

Change-Id: I5df61d9d17cf24ce9b58bebbefb610b7043fc39c
Closes-bug: #1404820
Merge "Bump API version to 2.3"