Prevent uncommitted activity visibilities

There are some degenerate cases (in tests currently) where
visibility is changed unexpectedly in the finishTransaction.
These are incorrect, but to make things a little more robust
and also to prevent unrelated changes from breaking tests,
add a failsafe mechanism.

Bug: 279672199
Test: atest NexusLauncherTests (need to run whole suite cuz
      it just happens randomly, not due to a specific test).
Change-Id: I19da051c0f6a476f61578cc5554c7b0eb2a66644