Watcher applier should be able to live migrate instances on any storage
type. To do this watcher will catch error 400 returned from nova if we
try to live migrate instance which is not on shared storage and live
migrate instance using block_migrate.
Added unit tests, changed action in watcher applier.
Closes-bug: #1549307
Change-Id: I97e583c9b4a0bb9daa1d39e6d652d6474a5aaeb1