implement two changes to better handle, identify, and recover from

implement two changes to better handle, identify, and recover from
situation where no detected network driver is found. this should prevent
machines from installing, and booting, only to become unresponsive due to
no loaded network driver.

the two changes are:
1. write out modprobe.conf at each boot, instead of only after install
2. if no network devices are written to modprobe.conf during boot,
send a message to the tech contacts about missing net driver, and
put the node into debug.