[RFC] channels regression issue

It was observed that with an updated version of libssh we see a timeout in the netopeer2-cli when connecting via ssh. This timeout appears after about 20 seconds of inactivity a new cli command is executed. Since this issue was not seen with libssh 0.9.2 I started some some debug/bisect and I figured out that setting the rc variable to the len value before checking "> 0" solves the issue.