onDestroy, remove messages+callbacks on handler

Messages in the the KeyguardUpdateMonitor handler were still being
called after a test was finished, causing an assertMainThread exception
while running tests sometimes, so we would see flaky tests.

Test: atest SystemUITests
Fixes: 150592614
Change-Id: Ibd25e09948711054a4ef144cb54eaacfe566eeca
1 file changed