slapproxy: Add missing instance parameters

slapproxy, just like reference SlapOS Master, has to transmit important
partition parameters, in order to really support all features expected by the
software releases.
3 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
failed SlapOS-Master.UnitTest-Master

01:23:33

failed SlapOS.Eggs.UnitTest-Master.Python2

00:11:51

failed SlapOS.Eggs.UnitTest-Master.Python3

00:15:01