don't call on_fail during shutdown also

coolamqp/clustering/cluster.py

@@ -259,7 +259,7 @@ def shutdown(self, wait=True):  # type: (bool) -> None
         :param wait: block until this is done
         :raise RuntimeError: if called without start() being called first
         """
-
+        self.connected = False
         try:
             self.listener
         except AttributeError: