Add retry and queue size on async producer

[ashangit]

Add retry on async producer in case of send failure. Default set to 3
retry with a back retry set to 300 ms

Add capabilities to limit the size of the async queue in order to avoid
having too much memory consumption by this queue if the async process
is not able to send messages fastly.

[wizzat]

Shouldn't this break be in the try?

[ashangit]

In the try or out the try do the same.
We continue if we face an exception or we break if no exception.

[toli]

What's the status of this PR? it's been 4+ months, same with #304
We are facing a similar problem at at work, and i'd prefer not to have custom patches and just use vanilla upstream code...

@dpkp - you mentioned something about Rdio having their own, perhaps you can get that committed to upstream? or get this patch in?

[dpkp]

I'd like to get #331 merged for this issue instead. If you have a second to review, would appreciate more eyeballs and/or testing.

[dpkp]

#331 is merged and supports this via async_queue_maxsize and async_queue_put_timeout configuration parameters to the producer