Enable WSL logins bouncer for self- or admin-created accounts when bouncer registration disabled

Submitting the fix suggested by knsheely on the wordpress.org WSL support forum: http://wordpress.org/support/topic/setting-accept-new-registration-to-no-restricts-current-users-from-logging-in. It works great for me.

The most important benefit is that it enables invitation-only sites to integrate WSL, where accounts are created by admins.

Thanks!