s3:smbd/service: switch load_registry_service/shares to use loadparm routines

s3:smbd/service: switch load_registry_service/shares to use loadparm routines

instead of reading the registry directly with tdb and activating the
configure options by hand.

This eliminates the need for repeating checks done in loadparm.
For instance it disables registry shares without path in the server
as is the case with text based shares.

Michael