Core/AI: Clean up charm AI handling.

Port From (https://github.com/TrinityCore/TrinityCore/commit/e4e8c1c59c8b37216814526b4d2551f23934f465)

Source/Scripts/Spells/Generic.cs

@@ -1549,7 +1549,7 @@ namespace Scripts.Spells.Generic
             GetUnitOwner().GetAllMinionsByEntry(minionList, CreatureIds.EtherealSoulTrader);
             foreach (Creature minion in minionList)
             {
-                if (minion.IsAIEnabled)
+                if (minion.IsAIEnabled())
                 {
                     minion.GetAI().Talk(TextIds.SayStealEssence);
                     minion.CastSpell(eventInfo.GetProcTarget(), SpellIds.StealEssenceVisual);

Source/Scripts/Spells/Quest.cs

@@ -327,8 +327,8 @@ namespace Scripts.Spells.Quest
                 if (!creatureTarget.IsPet() && creatureTarget.GetEntry() == _originalEntry)
                 {
                     creatureTarget.UpdateEntry(_newEntry);
-                    if (_shouldAttack && creatureTarget.IsAIEnabled)
-                        creatureTarget.GetAI().AttackStart(GetCaster());
+                    if (_shouldAttack)
+                        creatureTarget.EngageWithTarget(GetCaster());
 
                     if (_despawnTime != 0)
                         creatureTarget.DespawnOrUnsummon(_despawnTime);