Get dz safe return from cache not db

This was loading the dz from database to get safe return data every time
a client's dz removal timer triggered

Add the Zone::GetDynamicZone() method so zones that are dz instances can
find the data from the cache of any dz systems

zone/zone.h

@@ -33,6 +33,7 @@
 #include "spawn2.h"
 #include "spawngroup.h"
 #include "aa_ability.h"
+#include "dynamiczone.h"
 #include "pathfinder_interface.h"
 #include "global_loot_manager.h"
 
@@ -177,6 +178,7 @@ public:
 	void DumpMerchantList(uint32 npcid);
 	int SaveTempItem(uint32 merchantid, uint32 npcid, uint32 item, int32 charges, bool sold = false);
 	int32 MobsAggroCount() { return aggroedmobs; }
+	DynamicZone GetDynamicZone();
 
 	IPathfinder                                   *pathing;
 	LinkedList<NPC_Emote_Struct *>                NPCEmoteList;