Optimize test_volume_swap_with_multiattach for server status wait

The test creates two servers in serial and waits for each server
to go to ACTIVE status in serial. We can optimize this by creating
the two servers in parallel and waiting for them to be ACTIVE at
the same time.

Change-Id: Ia9c6db32789fd441b22d7431200283df22db3c59
1 file changed