vzncc: add -f FD option

If a program to run allows to specify a file descriptor to read from
and write to (ploop copy already does), we can keep its stdin/stdout
intact with this option.

This should help to see debug output from ploop copy (alas, sending
side only for now as receiving side stdout is redirected to /dev/null
by vzmigrate).

Signed-off-by: Kir Kolyshkin <kir@openvz.org>
2 files changed