Added method to Util module to clean up process records...

 that don't have a matching heartbeat record, indicating that they're no longer alive.

Added call to this new util method in the `Scheduled::Poller.poll_interval`
method because the number of live processes is used as a multiplier for
the default wait interval.  Since the value for poll_interval is
memoized, this call to 'cleanup_dead_process_records' should only be
called once at startup.
I'm a little confused.  `Sidekiq.redis` doesn't return a redis connection, it execute a block with a connection.  It looks like `Sidekiq.redis_pool` returns the redis connection.

I'm also not seeing where `REDIS.current` is coming from.

I added simple tracking in the upcoming commit, if there's something else you're looking for let me know.