Add a new "UpdateWaitConditionHandle" resource

On Update, the WaitConditions are not waited on if the count of unique ids
have already been satisfied before. If you have a setup which is watching
for changes and re-sending the signals then, it simplifies things for
the stack update to wait for these to be completed before moving on.

Change-Id: Ibfadc6f9c436ce3d0f468a4e5560233f762038dd
Merge "Add a new "UpdateWaitConditionHandle" resource"