New description:
Allow existing queries to continue running when view definition is updated via "collMod" command.

Old description:
There's a common pattern used in reporting where all applications point to collection1 and meanwhile a new version called collection2 is being populated. When it's done, DBAs want to atomically "replace" collection1 with collection2.

This can be done with views, but since we don't support updating view definitions or creating views while dropping existing view definition, they would have to drop view and then re-create view which is not transparent to the applications.

This ticket is to track adding an option to createView to drop/overwrite existing view definition.