Fixed a flakey test

Since the test could be off the UI thread, cancelling
would not be synchronized properly.

Test: runtest -x packages/SystemUI/tests/src/com/android/systemui/statusbar/notification/NotificationInflaterTest.java
Change-Id: Icfb02b637b76cdfb853c88130eabddf75203909b
Fixes: 65031224
1 file changed