Yes, this is fugly, yet formatting of the backend.list output
is spread all over the place (including vmods via the vdi_list_f
callback), so until we decide it is worth spending time on separating
formatting from content, I see no other option than making the
field widths known to all vrt.

The route ahead will likely be to only generate json and make varnishadm
reponsible for formatting plain text output.