Remove flow control and fragmentation if run on TCP transport

When run with a TCP transport, we don't need MFC and FRAG(2). However, if we remove FRAG2, the bundler at the transport will drop a message if it exceeds max_bundle_size.

Let's therefore bypass message bundling when the transport is TCP (TCP has its own batching).

TODO: measure how this change affects performance on a 4 node cluster. If positive, commit it.