make the parent kill off it's children after it's main loop is finished.

This solves problem reported privately by Thomas Klausner, where the
regress test would take very very long to complete.

regress/sys/kern/lockf/lockf.c

@@ -140,6 +140,7 @@ main(int argc, char **argv)
 	for (i=0; i<nprocs; i++) {
 		printf("reap %d: ", i);
 		fflush(stdout);
+		kill(pid[i], SIGINT);
 		waitpid(pid[i], &status, 0);
 		printf(" status %d\n", status);
 	}