DeclineCandidate from Candidate includes wrong term

[schuster]

When a candidate responds to a RequestVote with DeclineCandidate, it should include its own term in the response instead of the request's term. This allows the candidate that sent the request to update its own term.

[schuster]

This got flipped in the VoteCandidate response in Candidate: the current implementation responds with the current term, whereas it should update its term with the one from the request and send that back instead.