Backport overlay security fix

Replacing app opps fix with the flag that is used
elsewhere.

Bug: 37442941
Test: Verified that toast and system overlay still goes
away on permission and a11y service capability screens.

Merged-In: I27d357b2aa61193380b7ef1dcc88bbac9553644e

Change-Id: Ib7a7251109ed0f125db2bd49f5fc0baa67207b5d