Add a remote candidate.

def addRemoteCandidate(self, candidate):
        """
        Add a remote candidate.
        """
        # FIXME: don't use private member!
        if not self._connection._remote_candidates_end:
            if candidate is None:
                self._connection.add_remote_candidate(None)
            else:
                self._connection.add_remote_candidate(candidate_to_aioice(candidate))