Fix 401 from auth_token middleware

Fix 401 from auth_token middleware

The openssl popen call to verify the token returns an error code
of 2 when a file doesn't exist. Normally this is caught and the
relevant file is downloaded, but monkeypatching os causes this
error code to be eaten and cinder to return a 401. Note that this
is likely a race condition that depends on exactly when greenthreads
are switching that is causing the return code from Popen to get
overwritten.

It is possible that this is exposing an underlying bug in eventlet
but the workaround is simply to make sure that we don't monkeypatch
os.

Fixes bug 1075838

Change-Id: I69ba75136e32e95c6fdf108f0c4fe21a5e3bdbe6