Fix broken UTs due to py3
Fix broken UTs due to py3

Changes str to bytes to fix some UTs.

Partially-Implements: blueprint designate-py3

Change-Id: Icb7803ce4853cd829c0d8fe6875371ee39cebbae

cneill/designate-testing,grahamhayes/designate,ionrock/designate,muraliselva10/designate,ionrock/designate,ramsateesh/designate,tonyli71/designate,openstack/designate,ramsateesh/designate,ionrock/designate,tonyli71/designate,cneill/designate-testing,openstack/designate,muraliselva10/designate,tonyli71/designate,muraliselva10/designate,grahamhayes/designate,cneill/designate-testing,openstack/designate,ramsateesh/designate,grahamhayes/designate