First implementation of bp/live-migration-resource-calc

Fix based on revewer's comment

upgraded the migration version
nova/db/sqlalchemy/migrate_repo/versions/069_block_migration.py

rebase on master

Change-Id: Ia762f8dec761c3d595bc6fcd39f127f6d92306d2

nova/scheduler/multi.py

@@ -20,7 +20,6 @@
 """
 Scheduler that allows routing some calls to one driver and others to another.
 """
-
 from nova import flags
 from nova import utils
 from nova.scheduler import driver
@@ -39,6 +38,7 @@ flags.DEFINE_string('volume_scheduler_driver',
 _METHOD_MAP = {'run_instance': 'compute',
                'start_instance': 'compute',
                'prep_resize': 'compute',
+               'live_migration': 'compute',
                'create_volume': 'volume',
                'create_volumes': 'volume'}