restrict Ceph as storage backend for Glance used with vCenter

- rename 'vcenter_alert' to 'cinder_vcenter_alert' so we can distinguish
  one message from another
- add restriction to glance in openstack.yaml
- add new alert 'glance_vcenter_alert'
- add restrictions for Storage block on Settings tab

Change-Id: Iffff38e540d098c8e92335ad27204af26d856bef
Closes-bug: #1351288
Merge "restrict Ceph as storage backend for Glance used with vCenter"