libcriu: introduce CRIU_COMM_BIN

In this mode libcriu will execute criu binary in swrk
mode, so users are not always obliged to run criu service
daemon.

Signed-off-by: Ruslan Kuprieiev <rkuprieiev@cloudlinux.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>