cfg: Fix cfg_get_node_addrs incorrect retype

node_ifs is array of totemip_addresses not sockaddr storage, so don't
try to retype it and use correct family field.

Also instead of using buf of PIPE_BUF use alloca to alloc really needed
space.

Signed-off-by: Jan Friesse <jfriesse@redhat.com>
Reviewed-by: Fabio M. Di Nitto <fdinitto@redhat.com>