Merge pull request #957 from VallariAg/fix-prometheus-subsystem_namespace_count

control/prometheus.py: yield subsystem_namespace_count

Author: VallariAg

control/prometheus.py

@@ -421,6 +421,7 @@ def collect(self):
         yield subsystem_metadata
         yield subsystem_listeners
         yield subsystem_host_count
+        yield subsystem_namespace_count 
         yield subsystem_namespace_limit
         yield subsystem_namespace_metadata
         yield host_connection_state