Update the requirements.txt to point to the real neutron repository
Update the requirements.txt to point to the real neutron repository

The Thin MLNX commit is in neutron
https://review.openstack.org/#/c/148614/ workaround in requirements.txt
should be removed

Closes-Bug:1418467

Change-Id: I936d7df96b5c07cccc7dcb93eae0c2427904b03f

openstack/networking-mlnx,stackforge/networking-mlnx,openstack/networking-mlnx,stackforge/networking-mlnx