Route table UI is broken

[mantasaudickas]

Hello,

it looks like v1.5.11 has a broken UI which displays route table: it has an additional column with url, but missing header (so 6 columns in header and 7 in body).

See:
https://github.com/fabiolb/fabio/blob/master/admin/ui/route.go#L84
https://github.com/fabiolb/fabio/blob/master/admin/ui/route.go#L99