Move class properties to instances for dhcp/test_agent.py
Move class properties to instances for dhcp/test_agent.py

Using class properties for tests always carries the risk of
conflicting use between test cases when tests are run in parallel.

Change-Id: I41034001a8674ad208c57f2f60266769390f924b
Related-Bug: #1569507

noironetworks/neutron,huntxu/neutron,mahak/neutron,openstack/neutron,sebrandon1/neutron,huntxu/neutron,igor-toga/local-snat,cloudbase/neutron,igor-toga/local-snat,eayunstack/neutron,cloudbase/neutron,sebrandon1/neutron,eayunstack/neutron,bigswitch/neutron,bigswitch/neutron,openstack/neutron,mahak/neutron,mahak/neutron,noironetworks/neutron,openstack/neutron