'l2gw' entrypoint for Neutron service_plugins

Provide a 'l2gw' entrypoint definition, to allow the activation
  of the service plugin in a more friendly syntax.

Change-Id: Ia86f1885a9c9284d8a854891937b56cc9d730399
Signed-off-by: Ricardo Noriega <rnoriega@redhat.com>

contrib/README_install_and_config_l2gateway_plugin.rst

@@ -55,4 +55,4 @@ sudo service neutron-server status
 neutron-server start/running, process 17876
 
 and also check service_plugins in neutron.conf file whether 
-networking_l2gw.services.l2gateway.plugin.L2GatewayPlugin is enabled or not.
+l2gw is enabled or not.

contrib/install_and_config_l2gateway_plugin.sh

@@ -85,7 +85,7 @@ echo installing $pck_name\_$pck_ver\_$architecture.deb
 dpkg -i  $pck_name\_$pck_ver\_$architecture.deb
 echo enter neutron.conf file path
 read neutron_conf
-l2gw_plugin=", networking_l2gw.services.l2gateway.plugin.L2GatewayPlugin"
+l2gw_plugin=", l2gw"
 while read line
 do
 if [[ $line == *"service_plugins"* ]]

devstack/settings

@@ -1,7 +1,7 @@
 # Devstack settings
 L2GW_DIR=$DEST/networking-l2gw
 L2GW_AGENT_BINARY="$NEUTRON_BIN_DIR/neutron-l2gateway-agent"
-L2GW_PLUGIN=${L2GW_PLUGIN:-"networking_l2gw.services.l2gateway.plugin.L2GatewayPlugin"}
+L2GW_PLUGIN=${L2GW_PLUGIN:-"l2gw"}
 L2GW_CONF_FILE=/etc/neutron/l2gateway_agent.ini
 L2GW_PLUGIN_CONF_FILE=/etc/neutron/l2gw_plugin.ini
 #NETWORKING_L2GW_SERVICE_DRIVER=L2GW:OpenDaylight:networking_odl.l2gateway.driver.OpenDaylightL2gwDriver:default

setup.cfg

@@ -35,6 +35,8 @@ neutron.db.alembic_migrations =
 neutronclient.extension =
     l2_gateway_connection = networking_l2gw.l2gatewayclient.l2gw_client_ext._l2_gateway_connection
     l2_gateway = networking_l2gw.l2gatewayclient.l2gw_client_ext._l2_gateway
+neutron.service_plugins =
+    l2gw = networking_l2gw.services.l2gateway.plugin:L2GatewayPlugin
 
 tempest.test_plugins =
     networking_l2gw = networking_l2gw.tests.tempest.plugin:NeutronL2gwTempestPlugin