title: AFNetworking: setImageWithURLRequest not setting image
body: <p>I'm trying to set an image on an <code>ImageView</code> using AFNetworking's <code>setImageWithURLRequest</code> on a tableViewCell.  If I do not include the <code>success</code> and <code>failure</code> blocks in the method like so: </p>
  
  <pre><code>[cell.thumbnailImageView setImageWithURL:url placeholderImage:nil]; 
  </code></pre>
  
  <p>Everything works perfectly and the image sets.  Unfortunately I need the blocks.  </p>
  
  <p>Here's what I currently have in <code>cellForRowAtIndexPath</code>: </p>
  
  <pre><code>if (self.images) { //check if the array of images is set, fetched from a URL
  
          NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString: [[self.images objectAtIndex:indexPath.row] objectForKey:@"tbUrl"]]];
  
          [cell.thumbnailImageView setImageWithURLRequest:request placeholderImage:[UIImage imageNamed:@"placeholder"] success:^(NSURLRequest *request, NSHTTPURLResponse *response, UIImage *image) {
                  NSLog(@"success"); //it always lands here! But nothing happens
          } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error) {
                  NSLog(@"fail");
          }];
  
      }
  </code></pre>