Goal: remove UNICAST3 when the transport is TCP.

• As UNICAST3 is absent, it is the order in which messages are sent by the bundler which determines the order in which they will be delivered at the receiver
• Messages must not get lost in the transport (sender or receiver side):
  • Concurrent connection establishment (JGRP-2684)
  • Physical address not found (JGRP-2685)
  • More: see sanity checks below
• Sanity checks in the transport:
  • RED needs to be absent
  • The thread pool has to have a CallerRuns rejection policy
  • If MaxOneThreadPerSender is used: make sure that the queue is unbounded (max_buffer_size=0), or create a bounded queue which blocks when full
• TBD: new MessageProcessingPolicy: regular messages are passed up directly, OOB messages are passed to the thread pool. This causes OOB messages to backup behind regular messages though...