Calling WaitForPodTerminatedInNamespace after testFlexVolume is useless because
the client pod that it waits for always gets deleted by testVolumeClient:
0fcc3dbd55/test/e2e/framework/volume/fixtures.go (L541-L546)
Worse, because WaitForPodTerminatedInNamespace treats "not found" as "must keep
polling", these two tests always kept waiting for 5 minutes:
Kubernetes e2e suite: [It] [sig-storage] Flexvolumes should be mountable
when non-attachable 6m4s
The only reason why these tests passed is that WaitForPodTerminatedInNamespace
used to return the "not found" API error. That is not guaranteed and about to
change.