Fix bug with isChangeReviewed()

Bug was introduced where reviews will remain bold on the UI even if
the user has already reviewed the change. This corrects the bug by
fixing the order in which the change messages are sorted in the
isChangeReviewed() method. Additionally, two tests were added to test
this functionality.

Change-Id: I5f946d251de6689a9090af059a01a1616933b07a
2 files changed