11286 ldap cce

The helper getAttributeSortedStringSet fails loudly on
properties which are not strings. Instead we get each
object and do our best to convert it into a String.

#### Testing ####

Guarantee that LDAP login and new user creation still works properly. Unfortunately, I've never seen this behavior in the wild so reproducing may be difficult. If possible, an integration test will be added. Alternatively, a user may be able to validate the commit.