[s1943] Avoid creature not respawning when not looted.

This occurs when corpse decay time is bigger than respawn time.
This is not blizzlike, to permit a creature respawn when its corpse still exist we need a complete rewrite of creature pool system.

(based on commit [12415] - 5c87c13)

Signed-off-by: Xfurry <xfurry@scriptdev2.com>