Compel needs a socket that lives in victim's net namespace.
CRIU creates this socket once for all the processes it works
with. For pure compel case the socket is created for each
new ctl.

travis-ci: success for compel: Contrinue improving library
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>