U4-6992 - fix server registration for new LB

src/Umbraco.Core/Constants-System.cs

@@ -26,6 +26,8 @@
             public const int DefaultMediaListViewDataTypeId = -96;
             public const int DefaultMembersListViewDataTypeId = -97;
 
+            // identifiers for lock objects
+		    public const int ServersLock = -331;
 		}
 	}
 }