Most of the related source-code to UDP network protocol is now dead code. UDP should be removed.

• Rewrite unit tests from UDP to TCP or loopback channels.
  • Review the UDP tests that uses add_outer_node ()to see if they can be written using the inproc channel.
• Remove everything UDP related.
  • Remove UDP implementation.
  • Remove no longer needed config options.
  • Remove related stats
  • Check there is no related unused function and structures.