Propagate OVS_DATAPATH_TYPE to ml2_conf.ini

If OVS_DATAPATH_TYPE is configured it should be visible in ML2 config

Changing OVS_DATAPATH_TYPE default value to 'system' from ''

Closes-Bug: 1499029
Change-Id: I88e7d2554e8a1d6dcfea71fc1fb8e9fb2491d8b7
diff --git a/lib/neutron_plugins/openvswitch_agent b/lib/neutron_plugins/openvswitch_agent
index 1ff3a40..48e47b3 100755
--- a/lib/neutron_plugins/openvswitch_agent
+++ b/lib/neutron_plugins/openvswitch_agent
@@ -105,6 +105,7 @@
         iniset "/$Q_PLUGIN_CONF_FILE.domU" agent root_helper "$Q_RR_COMMAND"
     fi
     iniset /$Q_PLUGIN_CONF_FILE agent tunnel_types $Q_TUNNEL_TYPES
+    iniset /$Q_PLUGIN_CONF_FILE ovs datapath_type $OVS_DATAPATH_TYPE
 }
 
 function neutron_plugin_setup_interface_driver {