SQS: Fix onQueue
SQS: Fix onQueue

The `onQueue` function was simply calling `createQueue` but if a
queue with the specified name already existed with a different
VisibiltyTimeout an error was being thrown.

Fix this by making `onQueue` call `getQueueByName` which tries to
get the queue and if it doesn't exist, create it.

ambiata/mismi,ambiata/mismi