Core/AI: No longer override chase movement with follow movement if the creature engages before JustAppeared has had a chance to fire.

Port From (https://github.com/TrinityCore/TrinityCore/commit/a4c2c0fb1d1b9fae832ecc52aa68fe3fb8d1ca52)

Source/Game/AI/CoreAI/CreatureAI.cs

@@ -185,6 +185,8 @@ namespace Game.AI
 
         // Called when creature appears in the world (spawn, respawn, grid load etc...)
         public virtual void JustAppeared()
+        {
+            if (!IsEngaged())
             {
                 TempSummon summon = me.ToTempSummon();
                 if (summon != null)
@@ -201,6 +203,7 @@ namespace Game.AI
                     }
                 }
             }
+        }
 
         public override void JustEnteredCombat(Unit who)
         {

Source/Game/Combat/ThreatManager.cs

@@ -59,9 +59,14 @@ namespace Game.Combat
             if (cWho.IsPet() || cWho.IsTotem() || cWho.IsTrigger())
                 return false;
 
-            // summons cannot have a threat list, unless they are controlled by a creature
+            // summons cannot have a threat list if they were summoned by a player
-            if (cWho.HasUnitTypeMask(UnitTypeMask.Minion | UnitTypeMask.Guardian) && !cWho.GetOwnerGUID().IsCreature())
+            if (cWho.HasUnitTypeMask(UnitTypeMask.Minion | UnitTypeMask.Guardian))
+            {
+                TempSummon tWho = cWho.ToTempSummon();
+                if (tWho != null)
+                    if (tWho.GetSummonerGUID().IsPlayer())
                         return false;
+            }
 
             return true;
         }