Fix bot chest looting exploits in ICC and Halls of Stone (#1280)

- Prevent bots from looting Gunship Armory chest in ICC before the event ends (#1162)
- Fix bots being able to loot Tribunal Cache in Halls of Stone multiple times (#1200)
- Ensure bots do not attempt to loot Deathbringer's Cache in ICC before it is available

Three chests (Gunship Armory, Tribunal Cache, Deathbringer's Cache) were tested and now behave as expected: bots will not approach or attempt to loot chests while they are unlootable, even if players move close to them.

Closes #1162, #1200

src/LootObjectStack.h

@@ -29,6 +29,7 @@ public:
     LootObject() : skillId(0), reqSkillValue(0), reqItem(0) {}
     LootObject(Player* bot, ObjectGuid guid);
     LootObject(LootObject const& other);
+    LootObject& operator=(LootObject const& other) = default;
 
     bool IsEmpty() { return !guid; }
     bool IsLootPossible(Player* bot);