Add seat-id parameter when call OpenSessionWithParameters from GdmSessionWorker

This change is fix console-kit-daemon crash when user login with added feature
"specify SEAT_ID when adding a new seat"

At the same time, quering GdmDisplay D-Bus interface is a better way to get
properties like display-type, seat-id. So I revert gdm_session_direct_new back
without display-type.