slapgrid: provide software instance reference to buildout

slapos/grid/SlapObject.py

@@ -614,6 +614,7 @@ class Partition(object):
         'templates/buildout-tail.cfg.in')) % {
             'computer_id': self.computer_id,
             'partition_id': self.partition_id,
+            'software_instance_reference': self.computer_partition.get("reference"),
             'server_url': self.server_url,
             'software_release_url': self.software_release_url,
             'key_file': self.key_file,

slapos/grid/templates/buildout-tail.cfg.in

@@ -15,6 +15,7 @@ key-file = %(key_file)s
 cert-file = %(cert_file)s
 shared-part-list =
   %(shared_part_list)s
+software-instance-reference = %(software_instance_reference)s
 
 [slap_connection]
 # Kept for backward compatiblity