cr-service.c: rm extra error messages

setup_opts_from_req() prints an error message, so there's no need
for its caller to print another one.

While at it, simplify/unify error checking, treating any
non-zero value as an error.

Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>