Use snapshots_client from tempest-lib

Below files have been migrated to tempest-lib-

 * snapshots_client.py: I7854f7e080de9e819a1fae0d2de5d3aee111505a
 * snapshots.py: I7854f7e080de9e819a1fae0d2de5d3aee111505a
 * test_snapshots_client.py: I7854f7e080de9e819a1fae0d2de5d3aee111505a

Now Tempest-lib provides above as stable interface
so Tempest should start using those from lib and remove its own copy.

Change-Id: Id28c615534235c345e31b895a77a53ceac4af1a4
4 files changed