To configure:

 * set system.netconsole.enabled to true
 * create system.netconsole.target dict
 * set a record with IP address and MAC and interface as subdict

It works with both static and DHCP interfaces, and applies online.
You could use bash-scripting in netconsole.conf.
You could override the MAC.

See tests/pillar/system.sls for further information.

Change-Id: I1cbde47575eb5d32a34cd6d79a063f42dbea7643