title: downloadProgress block in downloadTaskWithRequest is not called under AFNetworking 3.1.0 When downloading a gzip file
body: <p>I'm using AFNetworking 3.1.0 to download some pdfs from AWS S3. The only issue is that when the file is gzipped, the download progress block is not getting called.</p>
  
  <pre><code>NSURLSessionConfiguration *configuration = [NSURLSessionConfiguration defaultSessionConfiguration];
  AFURLSessionManager *manager = [[AFURLSessionManager alloc] initWithSessionConfiguration:configuration];
  
  NSURL *URL = [NSURL URLWithString:@"https://s3.amazonaws.com/awdtest/fullzip.pdf"];
  NSURLRequest *request1 = [NSURLRequest requestWithURL:URL];
  
  NSURLSessionDownloadTask *downloadTask1 = [manager downloadTaskWithRequest:request1 progress:^(NSProgress * _Nonnull downloadProgress)
  {
      NSLog(@"Progress: %f", downloadProgress.fractionCompleted);
  } destination:^NSURL *(NSURL *targetPath, NSURLResponse *response)
  {
      NSURL *documentsDirectoryURL = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:NO error:nil];
      return [documentsDirectoryURL URLByAppendingPathComponent:[response suggestedFilename]];
  } completionHandler:^(NSURLResponse *response, NSURL *filePath, NSError *error)
  {
      NSLog(@"File downloaded to: %@", filePath);
  }];
  [downloadTask1 resume];
  </code></pre>
  
  <p>Response headers:</p>
  
  <pre><code>HTTP/1.1 200 OK
  x-amz-id-2: CW06YcgIycOHZQy8bCJrT3aNfhatM9pty1mOjgYHumjCxRmNAQ+jhJHRQwl7mDIaQeTHI0fyrnU=
  x-amz-request-id: 105E010DECC91897
  Date: Sat, 14 May 2016 09:26:38 GMT
  Content-Encoding: gzip
  Last-Modified: Sat, 14 May 2016 09:21:29 GMT
  ETag: "88bbe0b318bf11dd56a31176d3384e78"
  Accept-Ranges: bytes
  Content-Type: application/pdf
  Content-Length: 1243325
  Server: AmazonS3
  </code></pre>
  
  <p>the progress block gets called if I use a non gzipped file: <a href="https://s3.amazonaws.com/awdtest/full.pdf" rel="nofollow">https://s3.amazonaws.com/awdtest/full.pdf</a></p>
  
  <p>Response headers:</p>
  
  <pre><code>HTTP/1.1 200 OK
  x-amz-id-2: gFOVfhheaMdeJOBb+7H8oaXjLLeOqlQl616XnYx6C2Gj7PBVLKZ9kMIN2fJOrGBcSgQ/7nbQOc0=
  x-amz-request-id: 26669D9B576E300A
  Date: Sat, 14 May 2016 09:54:58 GMT
  Last-Modified: Fri, 16 May 2014 05:42:35 GMT
  ETag: "6f16d7e09023ce8b50fd67abba7825c4"
  Accept-Ranges: bytes
  Content-Type: application/pdf
  Content-Length: 1411131
  Server: AmazonS3
  </code></pre>
  
  <p>I would appreciate any help.</p>
  
  <p>Thanks</p>