Fix AvatarPhotoControllerTest.

This fixes a test issue with internalCropUsedIfNoSystemCropperFound.

A bitmap must be created or the internal cropping will fail. This
wasn't picked up before because files from previous tests were not
being cleared properly - this also corrects that behaviour.

Bug: 223498130
Test: atest AvatarPhotoControllerTest
Change-Id: I3b550e94bea5894f984122bce420144355ea1cb4