Core/Pets: Do not force pets to follow their charmer when possessed by player

Port From (https://github.com/TrinityCore/TrinityCore/commit/8f02596162715b273b1a830425ae783bd00561c9)

Source/Game/AI/CoreAI/PetAI.cs

@@ -633,7 +633,7 @@ namespace Game.AI
 
         public override void OnCharmed(bool isNew)
         {
-            if (me.IsCharmed())
+            if (!me.IsPossessedByPlayer() && me.IsCharmed())
                 me.GetMotionMaster().MoveFollow(me.GetCharmer(), SharedConst.PetFollowDist, me.GetFollowAngle());
 
             base.OnCharmed(isNew);

Source/Game/Entities/Unit/Unit.cs

@@ -1239,6 +1239,11 @@ namespace Game.Entities
                     return;
         }
 
+        public bool IsPossessedByPlayer()
+        {
+            return HasUnitState(UnitState.Possessed) && GetCharmerGUID().IsPlayer();
+        }
+        
         public bool IsPossessing()
         {
             Unit u = GetCharmed();