Until now, we used a unique SetTopicOp class inside of ReceiveCommits,
which didn't have all the functionality of the SetTopicOp class. We now
move that class to server.change package to ensure to also use it by
ReceiveCommits. While at it, refactor to ensure we don't use TopicInput
entity in non-REST endpoints.
The test added a check that the onEditedTopic method was actually
called.
Bug: Issue 13522
Change-Id: I238fa64375bf445680893c0f69afb9a08e789dcc
08251ea6e7