Autofill: failing testClickCustomButton caused by fullscreen CL

Last fullscreen CL moved onClickListener from decor view to
RemoteView, that causes a regression in testClickCustomButton where
it sets a click listener on the RemoteView too.

Bug: N/A
Test: atest CtsAutoFillServiceTestCases:LoginActivityTest#testClickCustomButton
Change-Id: I5f9fe1383004476ddd1db224d937c99889725813