Allow admins to disallow queries on a table

[vrajat]

During certain scenarios, it is useful to disallow querying a table as data maybe inconsistent or not up to date. For example, a real time table is catching up on processing a stream of data.

One option is to add a flag to IdealState to disallow queries which can be set/unset through an API call.

[abhioncbr]

@Jackie-Jiang, can you please assign this to me? Thanks