Is it possible that there currently are no DNS entries that have been setup?
Another possibility is that if there *are* DNS entries, they've been entered at the controller's Profile level. In case you're not aware, the Profile settings are where you want to keep as many settings as possible. The override section will *override* a setting that exist in the main Profile. Normal use of the override section is for things like static IP addresses, hostnames, etc. Things that are unique to a device...and therefore not appropriate to enter into a common Profile.
In the UI, to get to the controller's Profile:
1) Configuration
2) Profiles
3) Double-Click on the Profile that is assigned to your RFS6000
4) Center column, expand Network and choose DNS.
If you don't see any DNS entries there either, then it would seem that the controller does not have any DNS entries. Does the controller need one? Or....are you really looking to assign DNS entries for the adopted APs?
Not sure why the password isn't working to access the CLI but works for the GUI. Maybe the management profile is configured to disallow CLI access?