Rewrite some methods using waitForResult (4/n)

We will be able to remove mLock since now all states are modified in the handler thread.

Bug: 145335013
Test: atest CtsRollbackManagerHostTestCases
Test: atest RollbackTest
Test: atest StagedRollbackTest

Change-Id: Id50f54e8315546e474bd482d67238fbac8b74767