parasite: the type of the communication socket must be SOCK_SEQPACKET

We use unix socket to communicate with parasite. Before we used
SOCK_STREAM, but it doesn't guaranty that the message boundaries will be
save.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>