Core/AI: Add some checks to catch if the AI changes mid-update for players.

Port From (https://github.com/TrinityCore/TrinityCore/commit/1015f307041b25b47a9bb4bc76ac4ed78c49d735)

Source/Game/Entities/Creature/Creature.Fields.cs

@@ -55,7 +55,6 @@ namespace Game.Entities
         bool m_AlreadySearchedAssistance;
         bool m_cannotReachTarget;
         uint m_cannotReachTimer;
-        bool m_AI_locked;
 
         SpellSchoolMask m_meleeDamageSchoolMask;
         public uint m_originalEntry;

Source/Game/Entities/Creature/Creature.cs

@@ -574,9 +574,7 @@ namespace Game.Entities
                     }
 
                     // do not allow the AI to be changed during update
-                    m_AI_locked = true;
-                    base.AIUpdateTick(diff);
-                    m_AI_locked = false;
+                    AIUpdateTick(diff);
 
                     if (!IsAlive())
                         break;
@@ -729,25 +727,12 @@ namespace Game.Entities
 
         bool DestoryAI()
         {
-            if (m_AI_locked)
-            {
-                Log.outDebug(LogFilter.Scripts, "DestroyAI: failed to destroy, locked.");
-                return false;
-            }
-
             SetAI(null);
             return true;
         }
 
         public bool InitializeAI(CreatureAI ai = null)
         {
-            // make sure nothing can change the AI during AI update
-            if (m_AI_locked)
-            {
-                Log.outDebug(LogFilter.Scripts, "InitializeAI: failed to init, locked.");
-                return false;
-            }
-
             InitializeMovementAI();
 
             SetAI(ai != null ? ai : AISelector.SelectAI(this));