hv_set_ifconfig does no input sanity checking

[David Medberry]

hv_set_ifconfig blindly trusts the input file provided to it. It doesn't validate that ipv4 addresses/netmasks/gateways are valid or self-consistent. Neither does it validate ipv6 info. It silently ignores the hwaddress (neither validating it nor setting it, simply assuring that it is present.)

Please add sanity checking with python's ipaddress module.

found in
0.3ubuntu2