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: I7c8d8b4143a5dd1cb684c31c4503608c8d5be0e3

Change-Id: I858f3585b2e7d334cddcf38bd0ac6481e778b6b6