mrd: only output evalID if found
mrd: only output evalID if found

If the multi-region job is a periodic/dispatch job, stopping them
returns an empty EvalID. This removes some unexpected empty lines.

dvusboy/nomad,dvusboy/nomad,hashicorp/nomad,hashicorp/nomad,dvusboy/nomad,burdandrei/nomad,hashicorp/nomad,burdandrei/nomad,burdandrei/nomad,dvusboy/nomad,hashicorp/nomad,hashicorp/nomad,dvusboy/nomad,burdandrei/nomad,burdandrei/nomad,burdandrei/nomad,dvusboy/nomad,dvusboy/nomad,burdandrei/nomad,hashicorp/nomad