Move Monkey patch back to being as early as possible

Commit 6ca8cb84fd moved the patching early in the loading process.
After some reshuffling in the agents, this might not be as early
as possible, so move them closer to their main()'s.

Change-Id: Ifddd3a3d87ef6cc06788e9b4c40d6a6d981ebe0c

neutron/agent/l3/agent.py

@@ -14,8 +14,6 @@
 #
 
 import eventlet
-eventlet.monkey_patch()
-
 import netaddr
 from oslo.config import cfg
 from oslo import messaging

neutron/agent/l3_agent.py

@@ -16,6 +16,9 @@
 
 import sys
 
+import eventlet
+eventlet.monkey_patch()
+
 from oslo.config import cfg
 
 from neutron.agent.common import config

neutron/agent/metadata/agent.py

@@ -18,8 +18,6 @@ import os
 import socket
 
 import eventlet
-eventlet.monkey_patch()
-
 import httplib2
 from neutronclient.v2_0 import client
 from oslo.config import cfg

neutron/agent/metadata_agent.py

@@ -14,6 +14,9 @@
 
 import sys
 
+import eventlet
+eventlet.monkey_patch()
+
 from oslo.config import cfg
 
 from neutron.agent.common import config as agent_conf