p.haul: p.haul-ssh

Currently we have such security holes:

1) All p.haul traffic goes without any encryption, which is
not safe at all, cosidering that attacker can easily peek memory pages
of migrating process.

2) p.haul-service binds to 0.0.0.0 and is accesible from the outside
for anyone who is trying to connect to it. So attacket can easily connect
to p.haul-service and migrate some malicious process to the server.

Lets solve that by using ssh wrapper for p.haul. It creates ssh tunnel
and transmits all p.haul traffic through encrypted channel.
It also allows user to optionally use built-in ssh compression, which
is useful when connection is very slow, but probably will only slow down
things on fast networks. Using ssh also gives us an ability to let our
wrapper start p.haul-service on dst(on 127.0.0.1, so it is not directly
accesible from the outer web) automatically, without having us to
start it in advance. Also, ssh allows us to solve keys\certificates
management problem in a very common way that is familiar to any system
administrator.

So, to migrate, lets say, a task with pid PID to dsthost, you need to
execute a single command:
$ p.haul-ssh pid $PID dsthost
p.haul: zdtm: use p.haul-ssh

Lets use p.haul-ssh to start p.haul-service
for us.