AI/SmartAI: Move SMART_EVENT_RESPAWN invocation from ::InitializeAI() to ::JustAppeared().

Port From (https://github.com/TrinityCore/TrinityCore/commit/e398bb16648b483c97a68b2a29b25173b2a71261)

Source/Game/AI/SmartScripts/SmartAI.cs

@@ -568,12 +568,6 @@ namespace Game.AI
 
             me.SetVisible(true);
 
-            if (!me.IsDead())
-            {
-                GetScript().ProcessEventsFor(SmartEvents.Respawn);
-                GetScript().OnReset();
-            }
-
             _followGuid.Clear();//do not reset follower on Reset(), we need it after combat evade
             _followDist = 0;
             _followAngle = 0;
@@ -583,6 +577,15 @@ namespace Game.AI
             _followCreditType = 0;
         }
 
+        public override void JustAppeared()
+        {
+            if (me.IsDead())
+                return;
+
+            GetScript().ProcessEventsFor(SmartEvents.Respawn);
+            GetScript().OnReset();
+        }
+
         public override void JustReachedHome()
         {
             GetScript().OnReset();