memsk: Keep on service and iters

The plan it to use this socket for images transfer, so keep it
outside of criu connection.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
img: Sync images via side channel, not vie rpyc socket

This does two things. First, optimizes the img sync time, since
we no longer toss the tar with images through python string IO.
Second, it simplifies the phaul service down to the state, when
we can stop using the rpyc and switch to another one (see next
patches).

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>