return org guid from db for user association list

To ensure backwards compatiblity with existing tools that
consume the user association API, we must return the
organization guid along with short and full names. This change
consumes the SQL query in oc_chef_authz that has also changed
to support this feature.
Merge pull request #108 from opscode/sd/acctmgmt-fix

return org guid from db for user association list