D8 site reinstall doesn't reuse existing settings.php settings.

When reinstalling an existing site (very common process during development), the existing settings for $settings['install_profile'], $databases['default']['default'], and $config_directories are not preserved like they were in d7, creating duplicate entries in settings.php.

I have a settings.php which uses $_ENV variables to setup the database, etc. Running the /core/install.php script or using `drush si --keep-config` script causes the new (duplicate) settings to be appended to the settings.php file.

Before re-installation

$databases['default']['default'] = array (
  'database' => getenv('DB_1_ENV_MYSQL_DATABASE'),
  'username' => getenv('DB_1_ENV_MYSQL_USER'),
  'password' => getenv('DB_1_ENV_MYSQL_PASSWORD'),
  'host' => getenv('DB_1_PORT_3306_TCP_ADDR'),
  'prefix' => '',
  'port' => '3306',
  'namespace' => 'Drupal\\Core\\Database\\Driver\\mysql',
  'driver' => 'mysql',
);
$settings['install_profile'] = 'config_installer';

$config_directories = array(
  CONFIG_ACTIVE_DIRECTORY => './../config/active',
  CONFIG_SYNC_DIRECTORY => './../config/staging',
);

$settings['bootstrap_config_storage'] = array('Drupal\Core\Config\BootstrapConfigStorageFactory', 'getFileStorage');

After reinstallation:

$databases['default']['default'] = array (
  'database' => getenv('DB_1_ENV_MYSQL_DATABASE'),
  'username' => getenv('DB_1_ENV_MYSQL_USER'),
  'password' => getenv('DB_1_ENV_MYSQL_PASSWORD'),
  'host' => getenv('DB_1_PORT_3306_TCP_ADDR'),
  'prefix' => '',
  'port' => '3306',
  'namespace' => 'Drupal\\Core\\Database\\Driver\\mysql',
  'driver' => 'mysql',
);
$settings['install_profile'] = 'config_installer';

$config_directories = array(
  CONFIG_ACTIVE_DIRECTORY => './../config/active',
  CONFIG_SYNC_DIRECTORY => './../config/staging',
);

$settings['bootstrap_config_storage'] = array('Drupal\Core\Config\BootstrapConfigStorageFactory', 'getFileStorage');
$databases['default']['default'] = array (
  'database' => 'drupal',
  'username' => 'drupal',
  'password' => '123',
  'prefix' => '',
  'host' => '172.17.0.44',
  'port' => '3306',
  'namespace' => 'Drupal\\Core\\Database\\Driver\\mysql',
  'driver' => 'mysql',
);
$config_directories['sync'] = 'sites/default/files/config_zfa3kMuN2171K6tY5u9A-8eOS0Wk9Uyv00aF7GcP7PTAMfL9-W7T0a4XQMPAfS2nbplbHbNpvA/sync';