Remove useless test dependency 'discover'
Remove useless test dependency 'discover'

Obsoleted by the unittest2 functionalities; see also:
http://lists.openstack.org/pipermail/openstack-dev/2015-August/073022.html

Change-Id: Icce63fd7ec5a480ae418bb2c6407942a78d2294a

openstack/sahara,zhangjunli177/sahara,crobby/sahara,tellesnobrega/sahara,egafford/sahara,egafford/sahara,crobby/sahara,crobby/sahara,openstack/sahara,zhangjunli177/sahara,tellesnobrega/sahara,zhangjunli177/sahara