[RESTRICT AUTOMERGE] Revert "Persist destroyed staged sessions until they are cleaned up"

Revert submission 16575908-dont_abandon_child_qt_dev

Reason for revert:  Reverting CVE-2021-39624 on qt-dev
Reverted Changes:
I4ede6b7a4:Persist destroyed staged sessions until they are c...
Ib0ba9f378:Don't abandon child sessions (1/n)

Change-Id: I50ab96061b2e0fa016a0fbdb5773ccc5f2397ac6
4 files changed