Core/Accounts: prevent existing account ban from being updated

Source/Framework/Constants/Language.cs

@@ -945,7 +945,8 @@ namespace Framework.Constants
         AccountBnetUnlinked = 1188,
         AccountBnetNotLinked = 1189,
         DisallowTicketsConfig = 1190,
-        // Room For More Level 3              1191-1198 Not Used
+        BanExists = 1191,
+        // Room For More Level 3              1192-1198 Not Used
 
         // Debug Commands
         DebugAreatriggerLeft = 1999,

Source/Framework/Constants/SharedConst.cs

@@ -957,7 +957,8 @@ namespace Framework.Constants
     {
         Success,
         SyntaxError,
-        Notfound
+        Notfound,
+        Exists
     }
 
     public enum WorldCfg