title: AFNetworking Expected content type error
body: <p>I am getting the json string in failure block    </p>
  
  <pre><code> NSURL *url = [[NSURL alloc] initWithString:@"http://www.vinipost.com/Services/Update/UpdateService.asmx/GetPropSubType?"];
          NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url];
          [AFJSONRequestOperation addAcceptableContentTypes:[NSSet setWithObject:@"text/html"]];
  
          AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
  
              NSLog(@"%@", JSON);
          } failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id JSON) {
              NSLog(@"Request Failed with Error: %@, %@", error, error.userInfo);
          }];
          [operation start];
  </code></pre>
  
  <p>Output: </p>
  
  <pre><code>Request Failed with Error: Error Domain=AFNetworkingErrorDomain Code=-1016 "Expected content type {(
      "text/json",
      "text/javascript",
      "application/json",
      "text/html"
  )}, got text/plain" UserInfo=0x71521a0 {NSLocalizedRecoverySuggestion=[{"PropTypId":1,"PropCatId":1,"PropTyp":"Flat/ Condo"}.......**
  </code></pre>