selftest: Show expected and actual return codes for test failures in fcnal-test

Capture expected and actual return codes for a test that fails in
the fcnal-test suite.

Signed-off-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20240124214117.24687-4-dsahern@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/fcnal-test.sh

@@ -109,6 +109,7 @@ log_test()
 	else
 		nfail=$((nfail+1))
 		printf "TEST: %-70s  [FAIL]\n" "${msg}"
+		echo "    expected rc $expected; actual rc $rc"
 		if [ "${PAUSE_ON_FAIL}" = "yes" ]; then
 			echo
 			echo "hit enter to continue, 'q' to quit"