ktls_tests: Log more details when a test fails.

• Make use of ATF_REQUIRE_INTEQ to log the values of integers for unexpected mismatches.

• Use ATF_REQUIRE_MSG in a few more places to log values when a requirement fails.

• Consistently use ATF_REQUIRE_ERRNO when checking for an expected errno value.

Reviewed by: markj
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D37691