roles/coturn: use new port_forwarding var prefix

roles/coturn/tasks/main.yaml

@@ -43,16 +43,16 @@
 - name: 'set-up port forwarding for listener'
   import_role: name='port_forwarding'
   vars:
-    rule_name: 'turn'
-    proto: 'tcp udp'
-    port: '{{ turn_port }}'
+    pf_rule_name: 'turn'
+    pf_proto: 'tcp udp'
+    pf_port: '{{ turn_port }}'
 
 - name: 'set-up port forwarding for relay'
   import_role: name='port_forwarding'
   vars:
-    rule_name: 'turn_relay'
-    proto: 'udp'
-    port: '{{ min_relay_port }}-{{ max_relay_port }}'
+    pf_rule_name: 'turn_relay'
+    pf_proto: 'udp'
+    pf_port: '{{ min_relay_port }}-{{ max_relay_port }}'
 
 - name: 'update coturn config'
   template: