Fix flaky TestTransitionDuringTransientTask* and Test_DeleteVersion_QueryAfterDeletion

[ShahabT]

Summary

• Fix flakes for Test_DeleteVersion_QueryAfterDeletion by putting the query step in the OnComplete of delete step to ensure their order.
• Fix TestTransitionDuringTransientTask by ensuring polling keep happening until TQ registration is complete. Extracted a helper called pollUntilRegistered and used in all places that could benefit from the improvement.