ifconfig cannot be pledged because of its overwhelming amount of

ifconfig cannot be pledged because of its overwhelming amount of
used ioctls. Furthermore due to the way the command line parser is
written it is difficult to apply the traditional first initialize then
pledge pattern.

unveil(2) gives us a different approach:
By veiling everything with unveil("/", "") and then locking down
unveil with unveil(NULL, NULL) we remove all filesystem access from
ifconfig kind of like giving a regular user a chroot without any
files.

OK deraadt