Improvement to schedular config file

[sushanthakumar]

Issue/Feature Description:
Currently schedular config file used for performance collection is a json file having an entry for each storage registered for storage. Each entry had storage id and metric parameters like below

{"storages": [{"id": "e744abbc-9bb2-41f9-bbc3-742bf294347f", "array_polling": {"perf_collection": true, "interval": 12, "is_historic": true}}]}

During storage delete, these entries need to be deleted. All the entries in array need to be traversed

Need to relook if this can be maintained as map of storage entries

Why this issue to fixed / feature is needed(give scenarios or use cases):
During storage delete, these entries need to be deleted. All the entries in array need to be traversed

How to reproduce, in case of a bug:

Other Notes / Environment Information: (Please give the env information, log link or any useful information for this issue)
Proposed solution: Backends which do not support query alert mechanism can throw unsupported feature exception so that user can handle accordingly

[sushanthakumar]

Addressed through #451, closing the issue