lib/neutron-plugins: Pass conf file parameter

The 'neutron_plugin_configure_l3_agent' function expects a path to a
configuration file as a parameter. This was not done for one call,
resulting in the generation of a 'DEFAULT' file in the DevStack
directory along with an invalid L3 configuration file. Resolve this.

Change-Id: I5781cb1ec4cfc1699e61dbc324d0bdb824b56be1
diff --git a/lib/neutron_plugins/services/l3 b/lib/neutron_plugins/services/l3
index 350aed8..0f0ed21 100644
--- a/lib/neutron_plugins/services/l3
+++ b/lib/neutron_plugins/services/l3
@@ -99,7 +99,7 @@
 
     _neutron_setup_interface_driver $Q_L3_CONF_FILE
 
-    neutron_plugin_configure_l3_agent
+    neutron_plugin_configure_l3_agent $Q_L3_CONF_FILE
 
     _move_neutron_addresses_route "$PUBLIC_INTERFACE" "$OVS_PHYSICAL_BRIDGE" True False "inet"