Logging for non-device modules extremely verbose

[kimburgess]

Currently the transport for device (TCP/UDP) modules has a pretty minimal approach to logging, only logging errors or warnings (eg connection thrashing). Debug logging of individual requests is instead left to the module itself rather than upstream transport.

This differs significantly for service modules and SSH modules. Transports for both of these log all TX and RX traffic, making things extremely verbose to the level where it hard to follow logs when monitoring a device. In the case of service modules this also leaks sensitive info (eg auth details) in requests.

Two possible ways to solve this that come to mind:

1. remove comms logging from transport_tcp and evented-ssh if it's no longer needed
2. put this logging behind a config flag that can be passed through from drivers if/when required.