Fixing devstack-gate failure
Fixing devstack-gate failure

 * Due to https://review.openstack.org/#/c/181478/1 python-nose
   is not installed by default anymore. Need to install it
   manually

Change-Id: Ie8bad1412cd1874a5cf3382d1ea17e71119afe1e

dennybaa/mistral,openstack/mistral,StackStorm/mistral,openstack/mistral,dennybaa/mistral,StackStorm/mistral