migration/colo: Optimize COLO primary node start code path

Optimize COLO primary start path from:
MIGRATION_STATUS_XXX --> MIGRATION_STATUS_ACTIVE --> MIGRATION_STATUS_COLO --> MIGRATION_STATUS_COMPLETED
To:
MIGRATION_STATUS_XXX --> MIGRATION_STATUS_COLO --> MIGRATION_STATUS_COMPLETED
No need to start primary COLO through "MIGRATION_STATUS_ACTIVE".

Signed-off-by: Zhang Chen <chen.zhang@intel.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>

migration/colo.c

@@ -666,8 +666,6 @@ void migrate_start_colo_process(MigrationState *s)
                                 colo_checkpoint_notify, s);
 
     qemu_sem_init(&s->colo_exit_sem, 0);
-    migrate_set_state(&s->state, MIGRATION_STATUS_ACTIVE,
-                      MIGRATION_STATUS_COLO);
     colo_process_checkpoint(s);
     qemu_mutex_lock_iothread();
 }

migration/migration.c

@@ -3613,12 +3613,7 @@ static void migration_iteration_finish(MigrationState *s)
         migration_calculate_complete(s);
         runstate_set(RUN_STATE_POSTMIGRATE);
         break;
-
-    case MIGRATION_STATUS_ACTIVE:
-        /*
-         * We should really assert here, but since it's during
-         * migration, let's try to reduce the usage of assertions.
-         */
+    case MIGRATION_STATUS_COLO:
         if (!migrate_colo_enabled()) {
             error_report("%s: critical error: calling COLO code without "
                          "COLO enabled", __func__);
@@ -3628,6 +3623,12 @@ static void migration_iteration_finish(MigrationState *s)
          * Fixme: we will run VM in COLO no matter its old running state.
          * After exited COLO, we will keep running.
          */
+         /* Fallthrough */
+    case MIGRATION_STATUS_ACTIVE:
+        /*
+         * We should really assert here, but since it's during
+         * migration, let's try to reduce the usage of assertions.
+         */
         s->vm_was_running = true;
         /* Fallthrough */
     case MIGRATION_STATUS_FAILED: