ChangeFinder has 2 findOne methods:
* findOne(String): Returns null if the change is not found
* findOne(Change.Id): Throws NoSuchChangeException if the change is not
found
Change both methods to return Optional<ChangeNotes> so that they are
consistent and callers are aware that they need to handle the case where
the change is not found.
Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: Ib6458b329cd8107e6472cd8b57e2c1696dd0da56
8be56c8074