Add support for microversion 3.51 that allows us to specify the
Availability Zone of the backup service that should create the backup.
New optional parameter available for "backup-create" when using
microversion 3.51 is "--availability-zone".
Depends-On: I595932276088d25abd464025c99dce33a2cc502b
Change-Id: Ia4bab5fcb95f6a8d1adb99c5d7dc1b3f7546c6f6