Add eventlet hacking check UT
Add eventlet hacking check UT

Adds UT that was accidentally removed in a revert.
See bug for more info.

Change-Id: Ie3e0755ba662c9d092f0a714715f2d4407402753
Closes-Bug: #1618205

openstack/neutron-lib,openstack/neutron-lib,openstack/neutron-lib,openstack/neutron-lib