Improve tracing and logging

Following changes are implemented:

- Use consistent levels for Open and Keepalive messages on rx/tx
- Add logging for bgp and xmpp peers getting send ready/blocked
- Remove unecessary logging from scheduling group code

Change-Id: Ieb36894d4d780ebe0535b76c33c3eaf10a6c7cb3
Merge "Improve tracing and logging"