Some file-type specific parameters can be fetched with
parasite code only, so lets carry parasite control block
pointer in struct fd_parms.

This is a bit ugly but requires less code to touch and
enough for now. In long terms we need some more generalized
routine/hooks which would depends on file type.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>