Raidsonic telnet

Hi @m-1-k-3, 

This pull request try to fix https://github.com/rapid7/metasploit-framework/pull/2188 with:

* Beautify code / styling like asked while code review
* Fix the way to establish a session over a telnet connection as we've discussed recently.

Hopefully changes are not breaking nothing, cannot test it! Let me know if it works for you, feel free to land once ready, so we can continue with review on  https://github.com/rapid7/metasploit-framework/pull/2188