Remove amqp default exchange hack

This change remove the hack to set the default exchange of a transport in the
amqp driver, by removing the usage of the configuration object to get the
default exchange in rabbit and qpid driver, and instead use the value
passed to the driver constructor into all amqp publishers and consumers
class/method that needs it.

Closes-bug: #1256345
Change-Id: Iba54ca79a49f8545854205c1451b2403735c1006
Merge "Remove amqp default exchange hack"