Can't schedule an import when the webhook is a WordPress-based site

Created by: MegaphoneJon

The various CMSes that CiviCRM supports all have different methods of indicating to their front page router which page should be loaded. Here are two examples:

Drupal: https://test-drupal.megaphonetech.com/civicrm/osdi/webhook
WordPress: https://testsite-wp.megaphonetech.com/wp-admin/admin.php?page=CiviCRM&q=civicrm%2Fosdi%2Fwebhook

Furthermore, this assumes that Drupal "clean URLs" are enabled. Otherwise, the Drupal URLs are constructed similarly:

Drupal (no clean URLs): http://example.org/index.php?q=civicrm/osdi/webhook
Joomla 1.5 sites: http://example.org/administrator/index2.php?option=com_civicrm&task=civicrm/osdi/webhook
Joomla 1.6+ sites: http://example.org/administrator/index.php?option=com_civicrm&task=civicrm/osdi/webhook
WordPress sites: http://example.org/wp-admin/admin.php?page=CiviCRM&q=civicrm/osdi/webhook

If it helps to troubleshoot, I provisioned a WordPress site at https://osdi3.megaphonetech.com on the same server as the other two.