rbovirt default instance first boot is to do a network boot instead of hard disk.
This could create issues is a boot server is found on the network and
could also slow instance boot from hard disk since the attempted network
boot has to fail before network boot is attempted.
The solution should be to make boot from HD the default first option
and to provide a 'first_boot_device' feature, similar to the 'user_data' feature.
The user who desires network/PXE boot will need to explicitly request it.