Add eventlet to requirements.txt
Add eventlet to requirements.txt

Change-Id: I413c446b4785b36a4cd7bb32c57f64d4815d640a
Closes-bug: 1339873

ramineni/my_congress,ekcs/congress,ekcs/congress,ekcs/congress,ekcs/congress,ramineni/my_congress,ramineni/my_congress,openstack/congress,openstack/congress,ramineni/my_congress