LDAP: specify appid when selecting from appconfig
LDAP: remove unnecessary func call, was a leftover from earlier refactor
LDAP: check first whether group exists in this backend before doing other operations
LDAP: check whether user exists for before trying to determine displayname
LDAP: avoid irritating log output
LDAP: user exists check on getHome, otherwise check will be performed with wrong configs on a multi LDAP server setup.