We should call Wait for grpc-proxy process stop before start. Otherwise,
the tcp port won't be released.
Fixes: #14926
Signed-off-by: Wei Fu <fuweid89@gmail.com>
This should aid in debugging test flakes, especially in tests where the process is restarted very often and thus changes its pid.
Now it's a lot easier to grep for different members, also when different tests fail at the same time.
The test TestDowngradeUpgradeClusterOf3 as mentioned in #13167 is a good example for that.
Signed-off-by: Thomas Jungblut <tjungblu@redhat.com>
