CinderRbdFlattenVolumeFromSnapshot controls whether cinder RBD volumes
created from a snapshot should be flattened in order remove a dependency
on the snapshot.
Depends-On: I430a2d1793ffcd0964d268a1930e3fb85e32a995
Change-Id: I4fb97b275c6288e81072d71d43f75f5b7aee1d6b