Modify NOVIRTNFSMOUNTS to allow mounts on vnodes with routable IPs.
This is different than the traditional behavior of this defs- variable. Previously it caused tmcd to not expose any NFS mounts to shared-host vnodes. We relax that now to allow exposing such mounts to vnodes with routable IP addresses. The rationale for this change is simply that the original option was only intended to prevent exporting mounts to hosts that could not reach the FS node anyway due to their unroutable cnet IPs.