Multithread optimization for object updater

This change makes the object updater work the same
as the container updater, which is that it now
spawns one thread for each node that it needs to
update. This should help optimize its
performance/efficiency.

Change-Id: If740b8c67c0d953e4b510913bd8594570d868da6
authors and changelog updates for 2.1.0 release

Change-Id: I457674f564dcacf0fd20004e9a3bb85113f53aa5
Merge "Multithread optimization for object updater"
Merge "authors and changelog updates for 2.1.0 release"