Hook_requirements in 'runtime' phase always triggers a variable_set

Hi there, thanks for this great module.

While debugging a performance problem for a client, I've come across this bit of code that looked strange to me:

  if ($phase == 'runtime') {
    $correct_key = variable_set('smart_ip_correct_ipinfodb_key', FALSE);
    if (!$correct_key) {
      $smart_ip_source = variable_get('smart_ip_source', 'ipinfodb_service');
      if ($smart_ip_source == 'ipinfodb_service') {
        // Generate an appropriate error message:
        // Missing API keys.
.......
.......

The logic within the whole block seems correct, but the problem is that variable_set() is incorrectly called at the beginning of it. It should be variable_get() instead:

$correct_key = variable_get('smart_ip_correct_ipinfodb_key', FALSE);

Otherwise, 2 things happen:

1.- a cache_clear_all is triggered for the variables in cache_bootstrap (as part of the variable_set() call).
2.- The logic of the conditional is always triggered because $correct_key evaluates always to FALSE (), since variable_set() returns nothing.

I'm attaching a patch for the Drupal 7 version of this. I'm not sure, but I think the problem exists for Drupal 8 too.