Registration plugin not adding a new user to a default group

[akrherz]

...Migrated from Ignite Jira OF-1265...

Happening with 1.7.0 version of this plugin. If one puts a name of a group into Default group field, then new users are not automatically put into that group (with in-band registration). Also, it probably should list a group somehow, because now when you hit save it doesn't show a Save message and it just shows the group in the input field.

I have also observed a side effect when it was adding new users to a bunch of random groups until i have tried to put a single group into this field.