Fixed an issue where test had lingering inflations

Because we are overriding the mainLooper and certain tests
had lingering inflations, when those inflation finished,
the main handler had been changed again.
We should really look into if this is 100% necessary in the
future but this should fix the flakey tests.

Fixes: 131413417
Test: atest SystemUITests
Change-Id: I761eace99cbedc2fa57e90016152c6d29b351dc2