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: I1a3e3c5b1696a5f5b95eac187acb5a03863b4a0b

Change-Id: If9bec515105369055415d54c7fcad7a65431f8e7