Fix the default volume api version

The volume v2 api was completely removed from cinder during Xena cycle.
Unfortunately we didn't update the api_version parameter, which defines
the cinder api version used, when we fixed the problem caused by
removal of volume v2 api[1].

This change fixes the outdated default and ensures the current v3 api
is used.

[1] 67acf2c5e95c46acbfd64aad20de6d26fdc66801

Change-Id: Id8940684c996e9c4bb615269976238d3f65e8140

magnum/conf/cinder.py

@@ -59,7 +59,7 @@ cinder_client_opts = [
                help=_('Type of endpoint in Identity service catalog to use '
                       'for communication with the OpenStack service.')),
     cfg.StrOpt('api_version',
-               default='2',
+               default='3',
                help=_('Version of Cinder API to use in cinderclient.'))
 ]
 

releasenotes/notes/fix-volume-api-version-908c3f1cf154b231.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Default value of ``[cinder_client] api_version`` has been updated from
+    ``2`` to ``3``, because volume v2 API is no longer available.