Wrap strcmp/wcscmp calls with ATF_CHECK_MSG and drop atf_tc_fail use

The reasoning here was the same as what was done in r313376:

• Gather as many results as possible instead of failing early and not testing the rest of the cases.
• Simplify logic when checking test inputs vs outputs and printing test result.

MFC after: 1 week
Sponsored by: Dell EMC Isilon