* Add rangeReqId so we can cancel all associated block req via single flag

* Use crypto/rand instead of math/rand for randomReqId

* Use atomic counter instead of random num for rangeReqId

* Remove redundant peerRequest.complete field. Use inFlight instead

* Add mutex to activeRangeRequests map

* Do not penalize peer for block not found error

* Fix inFlight request clean up logic

* Add test checks for cancelled range request

* Add mutex protection to inFlight map

* Use constants for ResultCode

* Simplify inFlight.get method logic

* Use same struct for activeRangeRequests and inFlight