Support legacy host inclusion in environments

[akarasulu]

Legacy infrastructure might not even be able to fit into a container. Non-container legacy infrastructure hosts should be able to join the environment swarm with a P2P client configuration on it.

This allows the use of containerized infrastructures while easily bridging legacy systems and services into an environment.

[soffokl]

Connecting legacy systems could be implemented by following ways:

1. The same way as we are connecting client machine (p2p+tray) for easy ssh;
2. The same way as we are connecting RH - p2p+ovs+vxlan;

The key problem that I see now is that p2p require changing secret key with some period. But on legacy system we do not have any client for updating p2p key, when it will be changed by SS or HUB.
We should think about this moment first, because once configured legacy system will stop working in a hour.

[crioto]

In both cases p2p is not involved by itself and doesn't require any changes. It should live as is with implementations listed above. Regarding the problem you outlined - again, p2p should not handle this, because it receive keys from outside. So maybe some additional software needs to be written to manage this. Like some extra client or shrinked version of an agent.

[akarasulu]

We can deal with the key exchange mechanism later. For now just think about it being handled already.