Cleanup WBE example to be simpler to understand

This makes the example simpler to follow and understand when
it is using threads, is in one file and just uses the simpler
in-memory kombu backend by default (it can still use the file
transport if configured to use it).

Change-Id: I7fe9758e3285e7f0a610482bf26322841fb22f39
Merge "Cleanup WBE example to be simpler to understand"