Add firecracker vsock at instance startup

[schaefi]

This commit adds the init code to create a vsock per instance. This is related to Issue #87

[schaefi]

@m-kat this is code I had created prior you taking over issue #87 The code here only adds the creation of the vsock per instance and not more. I found that firecracker does not cleanup the socket file on the host when the instance terminates. So firecracker-pilot needs to this. Other than that if you register /bin/bash as a flake you can test the socket communication with this patch as follows:

1. In the guest shell

   socat VSOCK-LISTEN:42,fork -

2. On the host

   socat - UNIX-CONNECT:/run/sci_cmd_24965.sock
   CONNECT 42

So some tasks are still open

• [ ] implement socket file cleanup in firecracker-pilot
• [ ] implement sending of socket "CONNECT ID" string in firecracker-pilot
• [ ] implement sending of command to socket in firecracker-pilot
• [ ] implement listen on socket in sci

[schaefi]

@m-kat feel free to merge this when starting your implementation