When a legacy protocol implementation returns, move its `status` and
`ip` results to the new `status-ipv4` and `ipv4` (or `status-ipv6` and
`ipv6`) properties.
Also remove the now-unused `status` variable definition, and remove
`ip` from the recap.
* Delete values from `$config{$h}` and `$recap{$h}` when resetting
values (as opposed to setting a falsy value).
* Delete values from `$config{$h}` and `$recap{$h}` when they are no
longer needed.
This is mostly done to improve the tests in `t/update_nics.pl`.
This is mostly to simplify tests, but it also improves readability.
The infrastructure changes in this commit also make it possible to
introduce a new `url` variable that defaults to `opt('server', $h)`
concatenated with `opt('script', $h)` so that we can start migrating
away from those user-unfriendly variables.
