lvm: unhandled exception when migrating volume

Catches the StopIteration exception if the destination volume group
does not exist when attempting to migrate a volume.

Change-Id: I0b5dd15e4c7198fe54abf1aa917a60554adcd568
Closes-Bug:  #1277512
Fix cinder-backup volume restore with ceph driver

Restore operations currently break if restoring to
the backup source volume, that volume is an rbd and
the associated backup was incremental.

Change-Id: Ieafe6ab2d1a15cad2b534a3aab0df29eb8591306
Closes-Bug: 1276977
Merge "Fix cinder-backup volume restore with ceph driver"
Merge "lvm: unhandled exception when migrating volume"
(Test commit) Change README to reflect Jio's fork of Cinder

Change-Id: I3f26c0a736e63725aec24ca2fa12c707b8e6460f