unknown_command: fix message handling

edmond/plugins/unknown_command.py

@@ -36,8 +36,7 @@ class UnknownCommandPlugin(Plugin):
             return False
         words = message.split()
         if len(words) == 0 or words[-1] != self.config["command_suffix"]:
-            self.signal_failure(event.target)
-            return True
+            return False
 
         query = " ".join(words[:-1])
         self.process_query(query, event.target)