Remove workaround for eventlet < 0.27.0

This code worked around a bug in eventlet[1] that has been fixed in
115103d5608cbe8f15df10e27eba1644f5364e95. The fix has been available in
every eventlet release since v0.27.0.

[1] eventlet/eventlet#592

Also remove the note about old pip's behavior because recent pip does
not require specific order in requirements files.

Co-Authored-By: Cyril Roelandt <[email protected]>
Change-Id: I5929bc35c3ffd8ad4d3088cb957eb6a47d3905d2

Author: kajinamit

magnum/cmd/__init__.py

@@ -18,9 +18,3 @@
 import eventlet
 
 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  # noqa
-import threading  # noqa
-orig_threading.current_thread.__globals__['_active'] = threading._active