Use the right subprocess based on os monkeypatch
Use the right subprocess based on os monkeypatch

This works around the following eventlet bug:

https://bitbucket.org/which_linden/eventlet/issue/92

by using the green version of Popen if os has been
monkeypatched. It also has the side effect of making the ssl
calls not block the reactor for workers that use eventlet.

Change-Id: I1457237f52310f0536fbcdcaa42174b17e8edbf5

varunarya10/keystonemiddleware