Suppress log when request is cancelled (#16691)

Author: Kahbazi

src/Servers/HttpSys/src/RequestProcessing/ResponseBody.cs

@@ -127,9 +127,12 @@ public override void Flush()
             var flags = ComputeLeftToWrite(data.Count, endOfRequest);
             if (endOfRequest && _leftToWrite > 0)
             {
+                if (!RequestContext.DisconnectToken.IsCancellationRequested)
+                {
+                    // This is logged rather than thrown because it is too late for an exception to be visible in user code.
+                    LogHelper.LogError(Logger, "ResponseStream::Dispose", "Fewer bytes were written than were specified in the Content-Length.");
+                }
                 _requestContext.Abort();
-                // This is logged rather than thrown because it is too late for an exception to be visible in user code.
-                LogHelper.LogError(Logger, "ResponseStream::Dispose", "Fewer bytes were written than were specified in the Content-Length.");
                 return;
             }
 
@@ -690,8 +693,8 @@ protected override unsafe void Dispose(bool disposing)
                     {
                         return;
                     }
-                    _disposed = true;
                     FlushInternal(endOfRequest: true);
+                    _disposed = true;
                 }
             }
             finally