Fixed kubelet deleting data from volumes on stop (#7317).

[jsafrane]

We must not clear the pod directory in killUnwantedPods(), volumes are still
mounted there at this time. There already is cleanupOrphanedPodDirs(),
called later in the SyncPods() sequence, which should remove these pod
directories.

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[vmarmol]

@jsafrane we want to move to a model where more things are done per-pod and have less of the "orphaned resource" work. Removing this would move against that direction. Do you have a pointer to an issue or can you describe the problem? I am not be understanding where the problem lies :)

[childsb]

This bug is currently a showstopper for two of the volume plugins:

#7360
#7317

[vmarmol]

Aaaaah I see what you mean, thanks for the context @childsb! LGTM

[vmarmol]

@jsafrane have you had a chance to run the storage-related e2e's?

We should consider adding an e2e for this as well.

[vmarmol]

I ran e2e with this change and came back clean :) merging, thanks @jsafrane!

Ran 36 of 41 Specs in 1126.593 seconds
SUCCESS! -- 36 Passed | 0 Failed | 1 Pending | 4 Skipped I0429 09:58:54.840736    7378 driver.go:96] All tests pass