Revert "Revert "Finish child sessions when verification/setPermi..."

Revert "Revert "Add session cleanup tests for multi-package sess..."

Revert submission 16378718-revert-16345090-bug207814969-WMAMJQGXAR

Reason for revert:
ag/16345160 and ag/16345090 should be innocent.
Forrest run passes with the CLs included on TOT:
https://android-build.googleplex.com/builds/abtd/run/L95800000952155623
https://android-build.googleplex.com/builds/abtd/run/L48000000952162188
https://android-build.googleplex.com/builds/abtd/run/L14400000952156498

Reverted Changes:
Icb1f05ee0:Revert "Add session cleanup tests for multi-packag...
I7366ee43c:Revert "Finish child sessions when verification/se...

Change-Id: I81d9f760f302eee8e4c935270da96dea166d2c3b