FC-73 Keep processing messages if 5xx error on SQS receive

SQS can sometimes give 5xx errors, though the SDK does retry if this occurs. When an 5xx error is returned, repeat the main loop anyway rather than stop processing.

Signed-off-by: Steffan Westcott <steffan.westcott@clicktravel.com>
I would say that WARN is better because no harm is done as we will pick up any messages we did. An ERROR would indicate that something has gone wrong with negative consequences but we are carrying on. FATAL would mean something that gone wrong, with negative consequences but we are unable to continue. Our Logentries alert system sends notifications on WARN.