soccr: add support for syn-sent sockets

For that we restore all sockets properties and then
disable the repair mode before calling connect() and
the kernel will sent a syn packet and move the socket
into the sys-sent state.

travis-ci: success for series starting with [01/21] build: install libnet-dev
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>