Make rollback-app support --staged-ready-timeout flag

Staged rollback should be waiting for pre-reboot verificatio to complete
by default.

Also added a test to ensure it's working properly.

Bug: 162958790
Test: atest StagedInstallInternalTest#testAdbRollbackAppWaitsForStagedReady
Change-Id: I5dcaabaa2ecf9a5e137773821dd5920a09629aeb