Wait for server termination in server affinity tests

These tests were not waiting for server termination and
leading to failures in another serial tests which expects
no server running on the compute nodes.
Using method from parent class which already waits for
server deletion.

Closes-Bug: #2097594
Change-Id: Iea6ea61c5b827be705777cca5b972a5441a69540
1 file changed