Output the diffs to standard error when comparing the expected vs the

obtained output from lastcomm instead of just printing out a summary, e.g.
"they differed".

This will make failures with results more apparent when running kyua debug,
kyua report-html, etc.

Differential Revision: https://reviews.freebsd.org/D7079 (as part of a larger diff)
MFC after: 1 week
Approved by: re (gjb)
Reviewed by: cem
Sponsored by: EMC / Isilon Storage Division

usr.bin/lastcomm/tests/legacy_test.sh

@@ -14,7 +14,7 @@ check()
 	shift
 	# Remove tty field, which varies between systems.
 	awk '{$4 = ""; print}' |
-	if diff -q - $1
+	if diff -a - $1 >&2
 	then
 		echo "ok $NUM"
 	else