Add a device into devfs to be fully managed by netcfg. Netcfg will discover
and install the device into the Netstack. We cannot assume that netcfg has
observed and installed the device as a result of this function, that
condition must be observed via the interfaces watcher.
Initialize a realm with a device that is owned by netcfg.
The device is discovered through devfs and installed into
the Netstack via netcfg. after_interface_up is called
once the interface has been discovered via the Netstack
interfaces watcher.