Closes-Bug: #1600044

handle case if contrail stanza is not defined for cluster in determining
if cluster has ext lb

Change-Id: Ia373d5e9ed6d31a00d1be1674e36d3872de105dd

src/server_mgr_main.py

@@ -3596,7 +3596,7 @@ def is_cluster_ext_lb(self, cluster):
         cluster_params = eval(cluster['parameters'])
         cluster_provision_params = cluster_params.get("provision", {})
         if cluster_provision_params:
-            cluster_params_lb = cluster_provision_params['contrail']
+            cluster_params_lb = cluster_provision_params.get("contrail", {})
             if cluster_params_lb.get('loadbalancer', None):
                 return True
         return False