pthread_revert

Revert part of to prevent memory leak
https://mail-index.netbsd.org/source-changes/2020/01/27/msg113341.html

diff -r 8023d94696b6 -r bc8c9fc3ce7c lib/libpthread/pthread.c
--- lib/libpthread/pthread.c
+++ lib/libpthread/pthread.c
@@ -462,9 +462,11 @@ pthread_create(pthread_t *thread, const 
 	if (!PTQ_EMPTY(&pthread__deadqueue)) {
 		pthread_mutex_lock(&pthread__deadqueue_lock);
 		PTQ_FOREACH(newthread, &pthread__deadqueue, pt_deadq) {
-			/* Still busily exiting, or finished? */
+			/* Still running? */
 			if (newthread->pt_lwpctl->lc_curcpu ==
-			    LWPCTL_CPU_EXITED)
+			    LWPCTL_CPU_EXITED ||
+			    (_lwp_kill(newthread->pt_lid, 0) == -1 &&
+			    errno == ESRCH))
 				break;
 		}
 		if (newthread)