[main] Ensure second deactivate blocks until deactivation

When it comes to deactivation where the various steps of boot
have to be carefully synchronized, we need to make sure that
the client doesn't return early.

src/main.c

@@ -760,7 +760,10 @@ on_deactivate (state_t       *state,
 {
   if (state->deactivate_trigger != NULL)
     {
-      ply_trigger_pull (deactivate_trigger, NULL);
+      ply_trigger_add_handler (state->deactivate_trigger,
+                               (ply_trigger_handler_t)
+                               ply_trigger_pull,
+                               deactivate_trigger);
       return;
     }