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
ef7ed8dcb2