migration: include migrate_dirty_bitmaps in migrate_postcopy

Enable postcopy if dirty bitmap migration is enabled.
Signed-off-by: NVladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: NJuan Quintela <quintela@redhat.com>
Reviewed-by: NJohn Snow <jsnow@redhat.com>
Reviewed-by: NFam Zheng <famz@redhat.com>
Message-id: 20180313180320.339796-8-vsementsov@virtuozzo.com

migration/migration.c

@@ -1508,7 +1508,7 @@ bool migrate_postcopy_ram(void)
 
 bool migrate_postcopy(void)
 {
-    return migrate_postcopy_ram();
+    return migrate_postcopy_ram() || migrate_dirty_bitmaps();
 }
 
 bool migrate_auto_converge(void)