Devstack Nuage Plugin correct the ovs_bridge parameter

This commit fixes the name of ovs_bridge parameter and the section it is set in nova.conf by the nuage plugin

Closes-Bug: 1390256

Change-Id: I63c929e827db10d0cf5450907a273d880fc757f6
Merge "Devstack Nuage Plugin correct the ovs_bridge parameter"
Merge branch 'master' of https://github.com/openstack-dev/devstack