Monkey patch original current_thread _active
Monkey patch original current_thread _active

Monkey patch the original current_thread to use the up-to-date _active
global variable. This solution is based on that documented at:
https://github.com/eventlet/eventlet/issues/592

Change-Id: I5c2fbe1827195d670a67dd62cdadce5ee3513ace
Closes-Bug: #1863021

openstack/senlin,openstack/senlin,openstack/senlin,stackforge/senlin,stackforge/senlin