When retrieving events from nested stacks, we used to do a query per
stack and thus get the stack that way. We changed it to do only one API
call, but didn't fix the way the stack name was set. We need to use the
event links to retrieve the stack name, instead of the root stack.
Closes-Bug: #1676896
Change-Id: I09ab1cc2c6aaab02036b124b1dfa561dd6132083