Adding ML2 port security plugin config option and template output

config.yaml

@@ -408,3 +408,7 @@ options:
       wait for you to execute the openstack-upgrade action for this charm on
       each unit. If False it will revert to existing behavior of upgrading
       all units on config change.
+  enable-ml2-port-security:
+    type: boolean
+    default: False
+    description: If True enables port security extension for ML2 plugin.

templates/icehouse/ml2_conf.ini

@@ -4,6 +4,10 @@
 # Configuration file maintained by Juju. Local changes may be overwritten.  
 ###############################################################################
 [ml2]
+{% if enable_ml2_port_security == 'True' -%}
+extension_drivers=port_security
+{% endif -%}
+
 {% if neutron_plugin == 'Calico' -%}
 type_drivers = local,flat
 mechanism_drivers = calico

templates/kilo/ml2_conf.ini

@@ -4,6 +4,10 @@
 # Configuration file maintained by Juju. Local changes may be overwritten.  
 ###############################################################################
 [ml2]
+{% if enable_ml2_port_security == 'True' -%}
+extension_drivers=port_security
+{% endif -%}
+
 {% if neutron_plugin == 'Calico' -%}
 type_drivers = local,flat
 mechanism_drivers = calico