zdtm: cleanup launcher output in case of passed test

Print PASS only once.
Signed-off-by: Stanislav Kinsbursky <skinsbursky@openvz.org>
Acked-by: Andrew Vagin <avagin@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm.sh

@@ -292,7 +292,7 @@ EOF
 		[ $sltime -lt 9 ] && sltime=$((sltime+1))
 	done
 	cat $test.out
-	cat $test.out | grep PASS || return 2
+	cat $test.out | grep -q PASS || return 2
 }
 
 case_error()