mobs get hitlocked even with 0 mob walk delay

Originally posted by [b]theultramage[/b]
http://www.eathena.ws/board/index.php?autocom=bugtracker&showbug=3312

I received a report that in recent revisions, mobs get frozen in place when receiving damage, even when walk delay is set to 0 in the configs.

We traced the cause back to r13774 (bugreport #3078). After a conversation with Skotlex, it was shown that the change contains a typo:

This makes units walk an extra cell if the flag is NOT set, however that is the complete opposite to how the code was intended to behave. The fix is to remove the negation so that the code behaves as described in its comments ("Enable walking if flag is set").