Bit: Don't ignore errors and crashes

Bit used to only see success results and failures (== assertion failures?),
and didn't see "errors" (other exceptions) and test process crashes.

Fixed it.

Now it also returns an error status code if there was a test failure.

Bug 64292779
Test: manual

Change-Id: Iaba93910d32abfc615ae595746a0e9be1108583a