proc0_post: Clear relevant thread stats directly

rufetch() has several other effects besides clearing these per-thread
stats most of which are explicitly discarded by the subsequent calls
to ruxreset().  Just clear the relevant stats directly instead.

Reviewed by:	olce, kib, markj
Differential Revision:	https://reviews.freebsd.org/D54050

sys/kern/init_main.c

@@ -643,7 +643,6 @@ static void
 proc0_post(void *dummy __unused)
 {
 	struct proc *p;
-	struct rusage ru;
 	struct thread *td;
 
 	/*
@@ -660,11 +659,15 @@ proc0_post(void *dummy __unused)
 		}
 		microuptime(&p->p_stats->p_start);
 		PROC_STATLOCK(p);
-		rufetch(p, &ru);	/* Clears thread stats */
 		ruxreset(&p->p_rux);
 		FOREACH_THREAD_IN_PROC(p, td) {
-			td->td_runtime = 0;
 			thread_lock(td);
+			td->td_incruntime = 0;
+			td->td_runtime = 0;
+			td->td_pticks = 0;
+			td->td_sticks = 0;
+			td->td_iticks = 0;
+			td->td_uticks = 0;
 			ruxreset(&td->td_rux);
 			thread_unlock(td);
 		}