Exposing ObjectRequestOperation completion blocks

In some app I get 401 status code because of user auth token expired. So I had to wrap things like that:
 1. Duplicate & backup previous operation
 2. Reauthorize user
 3. Replay previous operation

But has a reference bug has been fixed about completionBlock, I couldn't access anymore on blocks attached to the completion block.

### Example of operation retry wrapped along 401 status code:
```objc
+ (void) properlyManagageFailureWithOperation:(RKObjectRequestOperation *)previousOperation
                                        error:(NSError *)error
                                      failure:(void (^)(NSError *error))failure{
    if (previousOperation.HTTPRequestOperation.response.statusCode == 401) {
        [UserManager reauthorizeCustomWithSuccess:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) {
            NSMutableURLRequest *newRequest = [previousOperation.HTTPRequestOperation.request mutableCopy];
            [newRequest setAllHTTPHeaderFields:[[RKObjectManager sharedManager].HTTPClient defaultHeaders]];
            RKObjectRequestOperation *newOperation = [[RKObjectRequestOperation alloc] initWithRequest:newRequest
                                                                                   responseDescriptors:previousOperation.responseDescriptors];
            
            [newOperation setCompletionBlockWithSuccess:previousOperation.successBlock
                                                failure:previousOperation.failureBlock];
            
            newOperation.targetObject = previousOperation.targetObject;
            newOperation.mappingMetadata = previousOperation.mappingMetadata;
            [[RKObjectManager sharedManager] enqueueObjectRequestOperation:newOperation];
            
            dispatch_async(dispatch_get_main_queue(), ^{
                [[NSNotificationCenter defaultCenter] postNotificationName:AFNetworkingOperationDidFinishNotification object:previousOperation.HTTPRequestOperation];
            });
            
        } failure:^(NSError *error) {
            if (failure) {
                failure(error);
            }
        }];
        
    } else if(failure) {
        VLRError *vlrError = [VLRError newWithError:error];
        vlrError.originalOperation = previousOperation;
        failure(error);
    }
}
```