Description of problem:
Cannot add existing sub groups to groups or sub groups, can only
create new ones.

Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1. Log in as sitewide admin, go to Groups administration.
2. Open a Group, for example GroupA1 (in
CamdenUserGroups>CamdenSiteAdministrators>CamdenContentAdministrators).
3. Attempt to add an existing subgroup, for example SubgroupA3one.
4. Cannot browse to this so must type in name. 
  
Actual results:
New SubgroupA3one is created.

Expected results:
Existing SubgroupA3one is picked up, together with its own subgroups.

Additional info:
Add member lets you browse existing users. It could be useful if Add
sub group worked the same way and let you browse existing sub groups.