In TestOVSAgent, there are two tests where the OVS agent is
configured and started twice per test. Before the second call,
the agent should be stopped first.
Depends-On: https://review.opendev.org/667216/
Change-Id: I30c2bd4ce3715cde60bc0cd3736bd9c75edc1df3
Closes-Bug: #1830895
(cherry picked from commit b77c79e5e8)
(cherry picked from commit ff66205081)