title: NSURLSession memory leak
body: <p>Even after invalidate a NSURLSession, running a profile using Instruments, some classes (probably privates) called TubeManager, HTTPConnectionCache and HTTPConnectionCacheDictionary still alive in memory.</p>
  
  <p>Code snippet to reproduce:</p>
  
  <pre><code>NSURLSessionConfiguration* config = [NSURLSessionConfiguration defaultSessionConfiguration];
  NSURLSession* session = [NSURLSession sessionWithConfiguration:config];
  NSURLRequest* request = [NSURLRequest requestWithURL:[NSURL URLWithString:@"http://www.google.com"]];
  NSURLSessionDataTask* sessionDataTask = [session dataTaskWithRequest:request
                                                 completionHandler:^(NSData *data, NSURLResponse *response, NSError *error)
  {
      [session finishTasksAndInvalidate];
  }];
  [sessionDataTask resume];
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/mqeBw.png" alt="Instruments screenshot"></p>