Throw AssertionError not on the UI thread

Assersions such as assertFalse() called outside of the test thread
would make the test process crash and debugging diffucult when it
actually fails.

With this CL, InputConnectionBlockingMethodTest no longer does such
assersions on non test threads.

Bug: 129012881
Test: atest -c CtsInputMethodTestCases:InputConnectionBlockingMethodTest
Change-Id: Ia9c147cbb56e30094b190815163c5799243c8015
1 file changed