Correctly stop functional servers
Correctly stop functional servers

When running integration tests, the test suite starts real zaqar
servers. The tearDown class was not stopping those servers correctly,
which made the test suite re-use server instances when that was not
necessary, causing other tests to fail.

Change-Id: Ie701a8a609f8661c3607890c4b1b37ab110b155b
Closes-bug: #1383604

openstack/zaqar,openstack/zaqar,openstack/zaqar,openstack/zaqar