api microversion header should conform to new guidlines

[Scott DAngelo]

As outlined in this api-wg spec:
https://review.openstack.org/#/c/243414/

microversion headers should be of the form:
OpenStack-API-Version: [SERVICE_TYPE] 2.114

i.e OpenStack-API-Version: Cinder 3.22

Two extra headers are always returned in the response::

    OpenStack-API-Version: [SERVICE_TYPE]_version_number
    Vary: OpenStack-API-Version

And:

note: Servers must be prepared to deal with multiple
  OpenStack-API-Version headers. This could happen when a client
  designed to address multiple services always sends the headers it
  thinks it needs. Most Python frameworks will handle this by setting
  the value of the header to the values of all matching headers,
  joined by a ',' (comma). For example ``compute 2.11,identity
  2.114``.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/286901
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=ef7ed8dcb28e743edbd839261a948fa84089f8fa
Submitter: Jenkins
Branch: master

commit ef7ed8dcb28e743edbd839261a948fa84089f8fa
Author: scottda <email address hidden>
Date: Tue Mar 1 14:42:05 2016 -0700

    support new HTTP microversion header

    According to API working group guidelines:
    https://review.openstack.org/#/c/243414

    microversion headers should be of the form:
    OpenStack-API-Version: [SERVICE_TYPE] 2.114

    i.e OpenStack-API-Version: volume 3.22

    Two extra headers are always returned in the response:

        OpenStack-API-Version: [SERVICE_TYPE] version_number
        Vary: OpenStack-API-Version

    note: Servers must be prepared to deal with multiple
      OpenStack-API-Version headers. This could happen when a client
      designed to address multiple services always sends the headers it
      thinks it needs. Most Python frameworks will handle this by setting
      the value of the header to the values of all matching headers,
      joined by a ',' (comma). For example ``compute 2.11,identity
      2.114``.

    Closes-Bug: #1551941
    Change-Id: I658e54966c390b41e3b551dd9827606c2e013511

[Thierry Carrez (ttx)]

This issue was fixed in the openstack/cinder 8.0.0.0rc1 release candidate.