The previous ignore-carrier rules did not work well with dynamic IP
(dhcp/slaac) connections. Change the rule so that only static IP
connections can be activated when carrier is not present (but both
static and dynamic connections will remain up when carrier is lost).
Add a "monitor-connection-files" config option, which can be set to
"false" to disable automatic reloading of connections on file change.
To go with this, add a new ReloadConnections method on
o.fd.NM.Settings that can be used to manually reload connections, and
add an nm-cli command to call it.
