How to allow an OG group admin to create and add a user to a group?
I found a round about way. I made my own form with two values and a user_access('administer group') check. The first value is the group id and the second is the user name. 

In the myform_form_submit(), if the user name exists in the users table, I run og_group to subscribe that user. If the username does not exists and the user has not logged in, I add them to a queue as a key value pair of username and group id. 

When the user logs in, hook_user_login() searches through that queue to find any instance and if so, subscribes them to that group.