probes: Port distro probe to python3

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
bcfg2: Update get_probe_as_dict to support lists

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
probes: Introduce new networking probe

This deprecates the old location probe and replaces it by a new
networking probe.

This probe uses a (generated) file at /etc/bcfg2.netmap to detect what
sites and zones the machine is based on all its current IPv4 and IPv6
addresses.

The result is exported as groups and as probe data.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>
probes: Don't fail on missing ipaddr

Gracefully recover from a missing python3-ipaddr module, in this case
exit 0 and wait till the next run for the package to be installed on the
system.

Signed-off-by: Stéphane Graber <stgraber@ubuntu.com>