Mask l2gw agent from initial start up

The service of l2gw-agent restarts too quickly after package
installation with default/incorrect configuration and goes over
restart threshold, so systemd stops attempt to restart any further
causing state faulure.

Change-Id: I06db792622c4cd9e9b6e2cec14d7906e6acfac2c
diff --git a/neutron/agents/l2gw.sls b/neutron/agents/l2gw.sls
index 1029f1a..e55ad3b 100644
--- a/neutron/agents/l2gw.sls
+++ b/neutron/agents/l2gw.sls
@@ -12,13 +12,20 @@
   - require:
     - pkg: l2gw_agent_packages
 
+{%- if not grains.get('noservices', False) %}
+
+# TODO: use service.masked state instead once salt get updated to 2017.7.0+
+service.mask:
+  module.run:
+  - m_name: neutron-l2gateway-agent
+  - require_in:
+    - pkg: l2gw_agent_packages
+
 neutron-l2gateway-agent:
   service.running:
   - enable: true
-  {%- if grains.get('noservices') %}
-  - onlyif: /bin/false
-  {%- endif %}
   - watch:
     - file: /etc/neutron/l2gateway_agent.ini
 
 {%- endif %}
+{%- endif %}