Automatic merge from submit-queue
refactor pv e2e code to improve readability
**What this PR does / why we need it**:
Moved the helper functions out of _persistent_volumes.go_ to a new file, _pvutil.go_, in order to improve readability and make it easier to add new tests.
Also, all pod delete code now calls the same helper function `deletePodWithWait`.
**Release note**:
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NONE
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