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: I93ce7f11dcd8c1f01616580b65e5e581b775e8c5
Story: 2007614

sahara/utils/patches.py

@@ -40,6 +40,12 @@ def eventlet_monkey_patch():
     monkey_patch multiple times.
     """
     eventlet.monkey_patch(**EVENTLET_MONKEY_PATCH_MODULES)
+    # 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  # noqa
+    orig_threading.current_thread.__globals__['_active'] = threading._active
 
 
 def eventlet_import_monkey_patched(module):