add query cancel APIs on controller backed by those on brokers

[klsince]

Add query cancel APIs on controller to easily show running queries across the cluster and cancel them

Release Note

Added two controller APIs to show running queries and cancel query as identified by (brokerId, qureyId).

1. GET /queries: to show running queries as tracked by all brokers
2. DELETE /query/{brokerId}/{queryId}[?verbose=false/true]: to cancel a running query with the provided queryId on the targeted broker. The verbose is false by default, but if set to true, responses from servers running the query also return.

[Jackie-Jiang]

LGTM