Handling Exception where ES calls are intercepted by SIfi

[yojs]

SiFi intercepts ES calls to get information about ES requests. This is used in generating the PA metrics for shard and bulk requests and also in handling cluster state change notifications. The problem is if the metric generation code throws an exception, it will be bubbled up all the way to ES and in some case fail the user request.
This issues address this problem. We should attempt to handle all exceptions in the Sifi calls