During force_live_migration operation there are 2
checks of migration status, one on api layer and one on
compute side, second one requires rpc request to be done
and also to query the db. This check could be removed as additional
one doesn't guarantee that live_migration is not already completed,
also is very small window between api and compute side.
Target compute host is now taken from migration object rather
then instance.host field, which allows to guarantee that nova will not
pause already migrated instance.
Change-Id: I51585302e898251e26cbf311aeac38a0ec329001
86a8006202