You can export/import the local-userdb and the whitelist-db, if you log into the CLI of the controller you want to export from you can use the following command:
local-userdb export <filename>
This will export to the flash: and you can then copy the file from the flash: to another host via tftp, scp, sftp, etc.
Then from the "mynode" level, do a "copy" to get the file in the flash: of the AOS 8 environment.
Finally, run the "local-userdb import filename" command to import the entries into the database.
I believe this is done from the mobility master (mynode) level, as I attempted to whitelist some RAPs at a /md/<folder> level and it ended up in the whitelist-db on mynode. Since the MM is now the Control Plane, I believe all whitelisting takes place here, and the controllers are only the Data Plane of the network traffic.
NOTE** - The import option will overwrite an existing database, so be sure that if you have existing entries to merge them using a text editor prior to importing the file, see from the AOS 8 CLI:
"import - Use this command with CAUTION, it will Replace the existing users with the user entries from the imported file."
Please correct me if I'm wrong, but this is how I understand it at least in AOS 8.5.0.5.