
When qos plugin is defined in 'neutron_plugin_base' it should also be added to 'extension_drivers' at ml2_conf.ini. If not, neutron-server will not start, throwing the following error: "ExtensionDriverNotFound: Extension driver qos required for service plugin qos not found." Change-Id: I87839e8c0fb0db27b89538d10d0573e80235260a