Set correctly the messaging driver to use in tests

Depending of the order of the tests executions, the driver can be the
previous configured one. But some tests are written to work on a
specific driver

This change sets the fake driver by default.

It also removes useless mock in test_log_handler.

Change-Id: Ic49bb9aec2e537e55a98315eba8dc97fbb18f96b
Reduces the unit tests run times

This change reduces all rabbit delay related to retring calls.

Change-Id: Ie50f1a66aefde40d85c194729007182d4f6f6e0c
Dispath messages in all listeners in a pool

This change ensures that we have messages in each listener of
a pool.

Change-Id: I2bbb830760b7f9c271e6cebe2e3852e2a5a19722
Closes-bug: #1397338
Merge "Reduces the unit tests run times"
Merge "Set correctly the messaging driver to use in tests"