ldapscripts: Re-use config values from /etc/nslcd.conf

Currently in users module setup, we configure LDAP server URI and SASL auth mech for nslcd: https://github.com/freedombox/Plinth/blob/master/actions/users#L53

We also configure the LDAP server URI, SASL auth mech, suffix, user suffix, and group suffix for ldapscripts: https://github.com/freedombox/Plinth/blob/master/actions/users#L164

ldapscripts can read settings for LDAP server URI, suffixes, and SASL auth mech from /etc/nslcd.conf (see https://github.com/gerasiov/ldapscripts/blob/master/debian/patches/02_debian_config.patch).

So this task is to remove the unnecessary configuration for ldapscripts, where it can re-use the nslcd config.