Added version constraint for pika library, disabled respawn limit, removed deprecated debug_format tag

Pika 0.9.9+ has a horrible bug that causes Beaver to poll the CPU too frequently. This in turn causes heavy load on systems running on EC2. Pika 0.9.8 does not have this issue.

Lastly, debug_format has been deprecated and generates a warning by Logstash on startup. Fixed the template to address that.