Fix eventlet imports issue
Fix eventlet imports issue

With Ubuntu python package 2.7.12-1ubuntu0~16.04.3 and
evetlet < 0.22.0 there is some issue with eventlet monkey_patching.
This commit adds workaround solution ported from eventlet patch
https://github.com/eventlet/eventlet/commit/b756447bab51046dfc6f1e0e299cc997ab343701

Change-Id: Ia381c98116765903bf2652acd175251233df4e54
Closes-Bug: #1745013

openstack/neutron,huntxu/neutron,mahak/neutron,noironetworks/neutron,openstack/neutron,mahak/neutron,mahak/neutron,openstack/neutron,huntxu/neutron,noironetworks/neutron