net: config: Try to only use auto started interface

If the first network interface is down when the net config init
is run, then the IP addresses etc would be set to wrong network
interface. So when initializing the network, try to first find
a network interface that is auto started and use that to configure
IP addresses etc.

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>