cli: add connection track action

Add --track-state action which will track an ongoing connection and exit if either the connection was closed in a way which allows to re-connect immediately or if network registration has been regained.

This allows to use mmcli by OpenWrt's netifd in a similar way to the ppp process, and netifd will take care of restarting the interface once this process exits.

Authored-by: Daniel Golle daniel@makrotopia.org Signed-off-by: Florian Eckert fe@dev.tdt.de