This change does the following:
- cleans up the usage of get_events so that marker and limit are only
specified in their dedicated arguments, not also in event_args
(also, specifying only in event_args still works)
- first attempts server-side nested_depth support
- falls back to the old recursive approach if the response data lacks a
link with the ref root_stack
Since there is a fallback for old heat APIs, the client change can
land before or after the heat change
I27e1ffb770e00a7f929c081b2a505e2007f5d584
Change-Id: I43d12ec61ec359222184f07c170de3c97481f1ba
Closes-Bug: #1588561
31278ff5f7