getrusage: RUSAGE_THREAD should return ru_utime and ru_stime

Impact: task stats regression fix

Original getrusage(RUSAGE_THREAD) implementation can return ru_utime and
ru_stime. But commit "f06febc9: timers: fix itimer/many thread hang" broke it.

this patch restores it.
Signed-off-by: NKOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: NRoland McGrath <roland@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/sys.c

@@ -1627,6 +1627,8 @@ static void k_getrusage(struct task_struct *p, int who, struct rusage *r)
 	utime = stime = cputime_zero;
 
 	if (who == RUSAGE_THREAD) {
+		utime = task_utime(current);
+		stime = task_stime(current);
 		accumulate_thread_rusage(p, r);
 		goto out;
 	}