The snapshot_support extra spec has always meant two things: a driver
can take snapshots and create shares from snapshots. As we add alternate
snapshot semantics, it is likely that some drivers will want to support
snapshots and some of the new semantics while being unable to create new
shares from snapshots.
This work adds support to manila client for the new extra spec in manila
server, create_share_from_snapshot_support.
Depends-On: Ib0ad5fbfdf6297665c208149b08c8d21b3c232be
Implements: blueprint add-create-share-from-snapshot-extra-spec
Change-Id: I07b70f04e6fb2b5797557c4f4796c6883680eff3