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:
eventlet/eventlet#592

Change-Id: I4872169413f27aeaff8d8fdfa5cdaf6ee32f4680
Closes-Bug: #1863021

nova/monkey_patch.py

@@ -59,6 +59,13 @@ def _monkey_patch():
     else:
         eventlet.monkey_patch()
 
+    # Monkey patch the original current_thread to use the up-to-date _active
+    # global variable. See https://bugs.launchpad.net/bugs/1863021 and
+    # https://github.com/eventlet/eventlet/issues/592
+    import __original_module_threading as orig_threading
+    import threading
+    orig_threading.current_thread.__globals__['_active'] = threading._active
+
     # NOTE(rpodolyaka): import oslo_service first, so that it makes eventlet
     # hub use a monotonic clock to avoid issues with drifts of system time (see
     # LP 1510234 for details)