Mitaka Cinder added an API to return Versions from the base
endpoint URL:
http://<url>:8776/
This patch exposes that API for /v3 endpoint microversions 3.0 and
above with the command:
cinder api-version
Implements: blueprint add-get-server-versions
Change-Id: Ieb1a56b28188ec17946fe5564b28c165833ffc24