Show more neat messages about AMQP authentication problems

- try to repeat problem actions with 5 sec delay;
- change message type from error to warning for authentication problem.

Change-Id: I06c7ab9a7afd639b083ffa0d573aa87c7433b48b
Closes-Bug: #1306729
(cherry picked from commit 6ed4d5a2d59675a59bb3f5bc94851ff13a4a4468)
Merge "Show more neat messages about AMQP authentication problems" into stable/5.0