Improve test coverage for ApiBlock.php to 100%

Improve test coverage for ApiBlock.php to 100%

The code coverage tool still reports that line 50 ("$status,") is not
covered, but this is just a parameter to a function that is in fact
called and does show up as covered, so I'm pretty sure it's a bug.

I replaced a couple of sanity checks that reported "incomplete" on
failure with actual assertions so that the test would fail properly if
the sanity check failed.

The testing could still probably be expanded considerably.

Change-Id: Ib6ba7227af23bcb50c7e3bafb0b51395e8acf03f