Fix clustering-test app rpcs to add new data ensuring parents

Fix clustering-test app rpcs to add new data ensuring parents

The add-person rpc needs to pass true for ensureParents when adding
a person into the datastore. This ensures that it can be called on
an empty model.

Similarly when the CarBought notification is received and we try to
add a car-person to the datastore we need to do it with ensureParents
so that the data can be added to an empty model.

Change-Id: I551038298d635ff6daed0f5dae49a6eda86a24cb
Signed-off-by: Moiz Raja <moraja@cisco.com>