Fix indefinite looping while guessing head stepping rate.

The old stepping code uses the cylinder number from the disk's ID
Record to switch stepping rates.  Some disks this information is
non-conventional or intentionally wrong which can lead to the old
heuristic to make incorrect assumptions flipping the rate back
and forth.

The new approach limits still uses the ID record cylinder number,
but only when transitioning from step 2 to step 1 breaking the
loop.

cw2dmk.c

@@ -2448,11 +2448,10 @@ main(int argc, char** argv)
 	if (guess_steps) {
 	  if (track == 3) guess_steps = 0;
 	  if (steps == 1) {
-	    if ((track & 1) &&
-		(good_sectors == 0 ||
-		 cylseen == track - 1 || cylseen == track + 1)) {
+	    if ((track & 1) && (good_sectors == 0)) {
 	      msg(OUT_QUIET + 1,
 		  "[double-stepping apparently needed; restarting]\n");
+	      guess_steps = 0;
 	      steps = 2;
 	      if (guess_tracks) tracks = TRACKS_GUESS / steps;
 	      goto restart;