Check to make sure the firewalld client is connected before proceeding.

Fixes #1138

Original patch referenced in https://github.com/ansible/ansible/issues/6911 ( f547733b1f ) was undone by 6f2b61d2d8

system/firewalld.py

@@ -97,7 +97,10 @@ try:
 
     from firewall.client import FirewallClient
     fw = FirewallClient()
-    HAS_FIREWALLD = True
+    if not fw.connected:
+        HAS_FIREWALLD = False
+    else:
+        HAS_FIREWALLD = True
 except ImportError:
     HAS_FIREWALLD = False