openstack-ardana-gerrit: fix resource label
openstack-ardana-gerrit: fix resource label

The Jenkins jobs triggered by Gerrit patches must use
a set of Lockable Resources dedicated to Gerrit, labeled
`cloud-ardana-gerrit-slot`, whereas the periodic Gerrit
Jenkins jobs must use the same Lockable Resources as the
other periodic Ardana jobs, the ones `cloud-ardana-ci-slot`

SUSE-Cloud/automation,aspiers/automation,gosipyan/automation,gosipyan/automation,SUSE-Cloud/automation,gosipyan/automation,SUSE-Cloud/automation,aspiers/automation,SUSE-Cloud/automation,aspiers/automation,gosipyan/automation,aspiers/automation