Declare cinder::glance to set glance_api_version

Prior to syncing upstream cinder module, glance_api_version was set from
cinder::backend::rbd. New upstream moved this to cinder::glance.

Change-Id: Ied9f4308b998e9f345449e03a00221de41261e85
Closes-Bug: #1373096
Merge "Declare cinder::glance to set glance_api_version" into stable/5.1