Always set change status for ChangeAttributes

ChangeAttribute's status was only set upon extension of the
ChangeAttribute. As extension is only used for queries, the event
stream does not provide the change status. We now set the change
status when transforming a change to a ChangeAttribute. Thereby,
event stream consumers can for example detect whether or not an event
refers to a draft change, or a non-draft change.

Change-Id: I252eb5d757ab3575def7c75a033dbc5b9b6a2f4a
1 file changed