Fix worker key generation in kobo.hub.models.Worker.save().
Fix worker key generation in kobo.hub.models.Worker.save().

pombredanne/https-git.fedorahosted.org-git-kobo,release-engineering/kobo,pombredanne/https-git.fedorahosted.org-git-kobo,release-engineering/kobo,pombredanne/https-git.fedorahosted.org-git-kobo,release-engineering/kobo,release-engineering/kobo,pombredanne/https-git.fedorahosted.org-git-kobo