core (xmpp): fix message workflow interruption from trigger.

libervia/backend/core/xmpp.py

@@ -1383,10 +1383,16 @@ class SatMessageProtocol(xmppim.MessageProtocol):
             message_elt,
             async_point_d
         )
-        await async_point_d
+        trigger_ret_continue = await async_point_d
+
         if delayed_call.active():
             delayed_call.cancel()
             log.debug(f"delayed_call for {async_point_d} cancelled")
+
+        if not trigger_ret_continue:
+            # trigger returned False, we stop the workflow.
+            return
+
         try:
             data = self.parse_message(message_elt)
             # we now do all post treatments added by plugins