Fix SSH CLI when using custom "shell" option

This fixes SSH CLI when using the custom "shell" option.  It Also addresses compatibility issue with PuTTY.

The patch to ssh_cli was first submitted to the mailing list back in December:
http://erlang.org/pipermail/erlang-patches/2013-December/004499.html

Per @IngelaAndin, here is the pull request for it.
(http://erlang.org/pipermail/erlang-bugs/2014-July/004489.html)

I added tests for the ssh_cli.erl fix, but I need help with testing the return value of ssh_connection:handle_cli_msg()