Cannot load external CDN libraries

Complete code on: https://www.drupal.org/project/bootstrap_library

bootstrap_library.libraries.yml

<?php
bootstrap:
  remote: http://getbootstrap.com/
  license:
    name: MIT
    gpl-compatible: false
  js:
    /libraries/bootstrap/js/bootstrap.min.js: { minified: true }
  css:
    theme:
      /libraries/bootstrap/css/bootstrap.min.css: {}
      /libraries/bootstrap/css/bootstrap-theme.min.css: {}
  dependencies:
    - core/jquery

bootstrap-dev:
  remote: http://getbootstrap.com/
  license:
    name: MIT
    gpl-compatible: false
  js:
    /libraries/bootstrap/js/bootstrap.js: { }
  css:
    theme:
      /libraries/bootstrap/css/bootstrap.css: {}
      /libraries/bootstrap/css/bootstrap-theme.css: {}
  dependencies:
    - core/jquery

bootstrap-cdn:
  remote: http://getbootstrap.com/
  license:
    name: MIT
    gpl-compatible: false
  js:
    //maxcdn.bootstrapcdn.com/bootstrap/3.3.1/js/bootstrap.min.js: { type: external, minified: true }
  css:
    theme:
      //maxcdn.bootstrapcdn.com/bootstrap/3.3.1/css/bootstrap.min.css: { type: external }
  dependencies:
    - core/jquery

?>

bootstrap_library.module

<?php
/**
 * Implements hook_page_attachments().
 */
function bootstrap_library_page_attachments(array &$page) {
  // Use Libraries API to load the js & css files into header

  if (drupal_installation_attempted()) {
    return; // Don't add the JavaScript and CSS during installation.
  }
  static $already_added = FALSE;
  if ($already_added) {
    return; // Don't add the JavaScript and CSS multiple times.
  }
  if (!_bootstrap_library_check_theme() || !_bootstrap_library_check_url()) {
    return; // Don't add the JavaScript and CSS on specified paths or themes.
  }
  $config = \Drupal::config('bootstrap_library.settings');
  $cdn = ($config->get('cdn.bootstrap'));
  if ($cdn) {
    $page['#attached']['library'][] = 'bootstrap_library/bootstrap-cdn';
  }
  else {
    $variant = ($config->get('minimized.options')) ? 'minified' : 'source';
    // Add and initialise bootstrap.
    if ($variant == 'minified') {
      $page['#attached']['library'][] = 'bootstrap_library/bootstrap';
    }
    else {
      $page['#attached']['library'][] = 'bootstrap_library/bootstrap-dev';
    }
  }
  $already_added = TRUE;
}

/**
 * Implements hook_library_info_alter().
 */
function bootstrap_library_library_info_alter(array &$libraries, $module) {
  if ($module === 'bootstrap_library' && isset($libraries['bootstrap'])) {
    $config = \Drupal::config('bootstrap_library.settings');
    $cdn = ($config->get('cdn.bootstrap'));
    if ($cdn) {
      $cdn = ($config->get('cdn.bootstrap'));
      $data = ($config->get('cdn.options'));
      $cdn_options =  json_decode( $data );
      $list = _bootstrap_library_object_to_array($cdn_options->bootstrap);  
      $libraries['bootstrap']['js'][0] = $list[$cdn]['js'];
    }
  }
}

?>

Thanks for the quick response!!!
To reproduce the problem:
Install bootstrap_library on a clean Drupal 8 installation. Use DEV version http://ftp.drupal.org/files/projects/bootstrap_library-8.x-1.x-dev.tar.gz
Install local bootstrap on /libraries/bootstrap folder
There are three options for loading bootstrap libraries:

1. Local minimized
2. Local non minimized
3. CDN

First two local versions load with no problem.
But CDN version does not load, it is not added to the javascript pool.
Tried two options, neither worked:

• Load the CDN library declared on bootstrap_library.libraries.yml.
• Declare the library via hook_library_info_build().

Declare CDN libraries on libraries.yml and did not work, this is the declaration:

bootstrap-cdn:
  remote: http://getbootstrap.com/
  license:
    name: MIT
    gpl-compatible: false
  js:
    //maxcdn.bootstrapcdn.com/bootstrap/3.3.1/js/bootstrap.min.js: { type: external, minified: true }
  css:
    theme:
      //maxcdn.bootstrapcdn.com/bootstrap/3.3.1/css/bootstrap.min.css: { type: external }
  dependencies:
    - core/jquery

Is this a bug??

This is how I am calling the library.
$page['#attached']['library'][] = 'bootstrap_library/bootstrap-cdn';
Is this what you mean?
It works perfect with local libraries, but not for CDN

JS aggregation is disable to check what is being loaded.
The file is not declared.
Tried also with http: included before, but as I said, file is not declared.
Installed mathjax and it is loading external files, compare codes and look the same.

Yes thanks for the patch, corrected what you mention with no success.
But did you get it to work?
I did not.

Yes!!!
Finally working.
Need to do a fresh installation, configuration was glued.
Clear cache several times with drush and no success.
Still an issue here I will address later.
Thanks you all guys.