fixes #5222 - Log ldap attributes in debug-level logging

Helps to see the whole process.  Looks like this:

```
LDAP-Auth with User uid=foreman,cn=sysaccounts,cn=etc,dc=bitbin,dc=de
DN found for stbenjam: uid=stbenjam,cn=users,cn=accounts,dc=bitbin,dc=de
Retrieved LDAP Attributes for stbenjam: {:firstname=>"Stephen", :lastname=>"Benjamin", :mail=>"stephen@bitbin.de", :avatar_hash=>"5d2f0b335c4a1875a575445c6d12fb072c73c075"}
Authenticated user Stephen Benjamin against LDAP-astriaporta authentication source
```