rabbit: uses kombu instead of builtin stuffs

The rabbit driver have a custom code to reconnect to a broker,
to change the broker in HA configuration, to retry a to send
a message, to handle the interval between reconnection.

But all of that exists in kombu, so just use it.

Using the kombu Connection object with the url make also the rabbit
driver more generic.

Futher patches can rename rabbit* oslo.config options to a more generic
name and add a new driver entry_point 'kombu' to allow to use this driver
with any borker supported by kombu.

Change-Id: Id6b89d5448126ca652b46fe6ce5a9b3ed5839795
Updated from global requirements

Change-Id: Ic229d9afdaf01abeff54d1087c21c70b25dcb0dd
Merge "rabbit: uses kombu instead of builtin stuffs"