Minor code refactoring

SMBLibrary/SMB2/Commands/LogoffRequest.cs

@@ -22,7 +22,7 @@ namespace SMBLibrary.SMB2
 
         public LogoffRequest() : base(SMB2CommandName.Logoff)
         {
-            StructureSize = 4;
+            StructureSize = DeclaredSize;
         }
 
         public LogoffRequest(byte[] buffer, int offset) : base(buffer, offset)

SMBLibrary/SMB2/Commands/LogoffResponse.cs

@@ -23,7 +23,7 @@ namespace SMBLibrary.SMB2
         public LogoffResponse() : base(SMB2CommandName.Logoff)
         {
             Header.IsResponse = true;
-            StructureSize = 4;
+            StructureSize = DeclaredSize;
         }
 
         public LogoffResponse(byte[] buffer, int offset) : base(buffer, offset)