Refactor test case for ml2 mech driver(remote port)
Refactor test case for ml2 mech driver(remote port)

This patch makes the test case atomic.

Change-Id: I6ff8e2a6b5048195166b55a731f324fce3e8c7e7
Partial-Bug: #1633078

openstack/dragonflow,openstack/dragonflow,openstack/dragonflow