fixes returning the base when multiple are specified

* reading the config directly will return the value with line breaks
* using the proper accessor gives us all bases in an array
* returns the first matching one
* having user id provided for the group base is strange and does not let
  us operate like this. here we return the first one. might change in
  future, a backportable fix won't have an API change however.

Signed-off-by: Arthur Schiwon <blizzz@arthur-schiwon.de>