Comment 3 for bug 1551955

Regression was introduced by this patch

  https://review.openstack.org/#/c/285265/8

where strict validation has been added. So now distance must be alway array while nailgun-agent sends 'nil' as its default value

  https://github.com/openstack/fuel-nailgun-agent/blob/01ec3c5501c4275063e81323116d4b65893a220f/agent#L867

Let's revert the patch with regression for now, and then reapply it when appropriate changes to nailgun-agent is commited.