Add more unit tests to mdns service
Add more unit tests to mdns service

Added tests to mdns service to cover udp calls

Change-Id: Ic330ada65904e0cc0f25ef8c5bd57e59c94178ed

cneill/designate-testing,tonyli71/designate,cneill/designate,cneill/designate,ramsateesh/designate,kiall/designate-py3,cneill/designate-testing,ionrock/designate,ramsateesh/designate,tonyli71/designate,cneill/designate,ionrock/designate,muraliselva10/designate,muraliselva10/designate,kiall/designate-py3,cneill/designate-testing,ionrock/designate,kiall/designate-py3,tonyli71/designate,ramsateesh/designate,openstack/designate,muraliselva10/designate,cneill/designate,grahamhayes/designate,kiall/designate-py3,cneill/designate,openstack/designate,openstack/designate,grahamhayes/designate,grahamhayes/designate,kiall/designate-py3