Displace a pet rather than stop travel

... and stop travel if you take damage from any source.

Original patch via Acehack by Alex Smith

src/uhitm.c

@@ -350,10 +350,12 @@ register struct monst *mtmp;
                 Strcpy(buf, y_monnam(mtmp));
                 buf[0] = highc(buf[0]);
                 You("stop.  %s is in the way!", buf);
+                context.travel = context.travel1 = context.mv = context.run = 0;
                 return TRUE;
             } else if ((mtmp->mfrozen || (!mtmp->mcanmove)
                         || (mtmp->data->mmove == 0)) && rn2(6)) {
                 pline("%s doesn't seem to move!", Monnam(mtmp));
+                context.travel = context.travel1 = context.mv = context.run = 0;
                 return TRUE;
             } else
                 return FALSE;