Set a timeout for splunk api requests.

Some of our more complicated queries take about 3 minutes, so I'm setting the limit at 5.

@jzoldak @mulby 
These names/comments are a bit off from the code.
Perhaps rename something along the lines of POLL_TRY_INTERVAL (wait time in seconds before trying again), POLL_TRY_LIMIT (maximum number of attempts to try)?