Divide vmware_nsx/services into plugin-specific subdirectories

This patch will create:
vmware_nsx/services/common for common plugin files
vmware_nsx/services/nsx_v3 for nsx_v3 specific plugin files

This is part of new vmware_nsx directory structure proposed in
https://goo.gl/GdWXyH.

Change-Id: I30753aef1c06e2a1b15d336e1d661f3b44ea669e

etc/nsx.ini

@@ -227,7 +227,7 @@
 
 # Specify the class path for the Layer 2 gateway backend driver(i.e. NSXv3/NSX-V).
 # This field will be used when a L2 Gateway service plugin is configured.
-# nsx_l2gw_driver = vmware_nsx.services.l2gateway.nsx_v3_driver.NsxV3Driver
+# nsx_l2gw_driver = vmware_nsx.services.l2gateway.nsx_v3.driver.NsxV3Driver
 
 [nsx_sync]
 # Interval in seconds between runs of the status synchronization task.

setup.cfg

@@ -32,7 +32,7 @@ neutron.db.alembic_migrations =
 neutron.core_plugins =
     vmware = vmware_nsx.plugin:NsxMhPlugin
 neutron.service_plugins =
-    vmware_nsx_l2gw = vmware_nsx.services.l2gateway.plugin:NsxL2GatewayPlugin
+    vmware_nsx_l2gw = vmware_nsx.services.l2gateway.common.plugin:NsxL2GatewayPlugin
     vmware_nsx_qos = vmware_nsx.services.qos.plugin:NsxQosPlugin
 vmware_nsx.neutron.nsxv.router_type_drivers =
     shared = vmware_nsx.plugins.nsx_v_drivers.shared_router_driver:RouterSharedDriver

vmware_nsx/tests/unit/vmware/services/l2gateway/test_nsxv3_driver.py

@@ -19,15 +19,15 @@ from neutron.tests import base
 
 from networking_l2gw.tests.unit.db import test_l2gw_db
 
-from vmware_nsx.services.l2gateway import nsx_v3_driver
-from vmware_nsx.services.l2gateway import plugin as l2gw_plugin
+from vmware_nsx.services.l2gateway.common import plugin as l2gw_plugin
+from vmware_nsx.services.l2gateway.nsx_v3 import driver as nsx_v3_driver
 
 from oslo_config import cfg
 from oslo_utils import uuidutils
 
 
-NSX_V3_DRIVER_CLASS_PATH = ('vmware_nsx.services.l2gateway.'
-                            'nsx_v3_driver.NsxV3Driver')
+NSX_V3_DRIVER_CLASS_PATH = (
+    'vmware_nsx.services.l2gateway.nsx_v3.driver.NsxV3Driver')
 
 
 class TestNsxV3L2GatewayDriver(test_l2gw_db.L2GWTestCase,