Fix one:
Fixed typo in defining `teleport.HOTP` constant.
This fixes bug #721
Fix two:
Removes 'drop tunnel connection' logic on any tunnel-related error. This
fixes 2nd problem "Handling Unreachable nodes" for issue #717 (see
klizhentas comment there)
- Added idle timeout handling to every SSH connection.
- A bit of code refactoring (removing unused code paths)
Most importantly:
Added a custom SSH handshake between SSH Teleport proxies
and SSH Teleport servers. This handshake sends a custom JSON payload
from a proxy to a server, allowing to exchange additional information,
like the true IP of a client.