Configure agents using neutron.common.config.init (formerly .parse)

After oslo.messaging port is done, we'll need to initialize RPC layer
from all RPC agents. We'll put initialization into init() function, so
the first step for migration is to make agents use it.

The function is renamed to be explicit about the fact that we don't just
parse configuration by calling it, but also do other common
initializations, like setting RPC layer.

blueprint oslo-messaging

Change-Id: I71c62f270ac7a1ff1426a3f49a32133b65580e35

neutron/agent/l3_agent.py

@@ -13,6 +13,8 @@
 #    under the License.
 #
 
+import sys
+
 import eventlet
 eventlet.monkey_patch()
 
@@ -26,6 +28,7 @@ from neutron.agent.linux import ip_lib
 from neutron.agent.linux import iptables_manager
 from neutron.agent.linux import ovs_lib  # noqa
 from neutron.agent import rpc as agent_rpc
+from neutron.common import config as common_config
 from neutron.common import constants as l3_constants
 from neutron.common import rpc_compat
 from neutron.common import topics
@@ -977,7 +980,7 @@ def main(manager='neutron.agent.l3_agent.L3NATAgentWithStateReport'):
     config.register_root_helper(conf)
     conf.register_opts(interface.OPTS)
     conf.register_opts(external_process.OPTS)
-    conf(project='neutron')
+    common_config.init(sys.argv[1:])
     config.setup_logging(conf)
     server = neutron_service.Service.create(
         binary='neutron-l3-agent',