Bamboo shouldn't try to add users in Crowd, when it doesn't have directory rights to add principals

When Crowd is configured not to let Bamboo manage users and groups, Bamboo still offers the possibility to create new groups. And if groups are being created in this way Bamboo will fail with an internal server error.

First off all if the service is disabled in Crowd then Bamboo should not offer the possibility to change groups. Second, if there is an attempt to create groups, a permission denied error would be more appropriate than a internet server error.