timed(8): Use stronger random number generator.

Using arc4random simplifies the code by not having to worry about
seeds which ironically depend on the time.

CID:	1300004

usr.sbin/timed/timed/timed.c

@@ -229,12 +229,9 @@ main(int argc, char *argv[])
 		exit(1);
 	}
 
-	/* choose a unique seed for random number generation */
+	sequence = arc4random();     /* initial seq number */
+
 	(void)gettimeofday(&ntime, NULL);
-	srandom(ntime.tv_sec + ntime.tv_usec);
-
-	sequence = random();     /* initial seq number */
-
 	/* rounds kernel variable time to multiple of 5 ms. */
 	ntime.tv_sec = 0;
 	ntime.tv_usec = -((ntime.tv_usec/1000) % 5) * 1000;