Covetous monsters will teleport to downstairs or upstairs

I accidentally swapped the covetous monsters teleport to stairs to heal
but instead of changing it back like it was, now make those monsters
teleport to either upstairs or downstairs - some of them will go up,
others go down.

doc/fixes3-7-0.txt

@@ -763,6 +763,7 @@ don't stop running when next to a peaceful, unless it blocks the way
 mindless monsters shouldn't cringe stepping on squeaky boards
 falling down a hole or trapdoor will cause damage proportional to fall height
 stinking gas clouds block line-of-sight
+covetous monsters will teleport to downstairs or upstairs to heal
 
 
 Fixes to 3.7.0-x Problems that Were Exposed Via git Repository

src/wizard.c

@@ -355,7 +355,7 @@ tactics(struct monst *mtmp)
     case STRAT_HEAL: /* hide and recover */
         mx = mtmp->mx, my = mtmp->my;
         /* if wounded, hole up on or near the stairs (to block them) */
-        choose_stairs(&sx, &sy, FALSE);
+        choose_stairs(&sx, &sy, (mtmp->m_id % 2));
         mtmp->mavenge = 1; /* covetous monsters attack while fleeing */
         if (In_W_tower(mx, my, &u.uz)
             || (mtmp->iswiz && !sx && !mon_has_amulet(mtmp))) {