Adding ioproc support for junos

Hi Leopoul,

I am trying to have ncclient onbox which doesn't require the SSH authentication.
I have created a ioproc session with native junos shell command('xml-mode netconf need-trailer') to invoke netconf session.
Kindly review the code, and let me know your comments.
This ioproc support helps in executing the python scripts onbox without username and password.

Thanks,
Kathar