Fix undefined variable.

Noticed by Benjamin.
(cherry picked from commit e51770f440db737f4904a24cb4d3180d422b0702)

stack/erp5/buildout.cfg

@@ -324,7 +324,7 @@ md5sum = 77ec4f095a22b5bd7dfea9dff63bade5
 [template-erp5-cluster]
 < = download-base
 filename = instance-erp5-cluster.cfg.in
-md5sum = f271a904e7cc0039ce109f592fb48b5f
+md5sum = ad80b47b39a3daaad89e102b95e14947
 
 [template-scalability]
 < = download-base

stack/erp5/instance-erp5-cluster.cfg.in

@@ -31,7 +31,7 @@ return = {{ ret.keys() | join(' ') }}
 {%     do publish_dict.__setitem__(name ~ '-' ~ ret, '${' ~ section ~ ':connection-' ~ ret ~ '}')%}
 {%   endif -%}
 {% endfor -%}
-sla-computer_guid = {{ slapparameter_dict.get(computer_guid_key + '-computer-guid', computer_id) }}
+sla-computer_guid = {{ slapparameter_dict.get(config_key + '-computer-guid', computer_id) }}
 extra-config = {{ ' '.join(config) }}
 {% for option, value in config.items() -%}
 config-{{ option }} = {{ dumps(value) }}