Function raftstore::store::util::is_first_vote_msg

fn is_first_vote_msg(msg: &Message) -> bool

is_first_vote_msg checks msg is the first vote (or prevote) message or not. It’s used for when the message is received but there is no such region in Store::region_peers and the region overlaps with others. In this case we should put msg into pending_msg instead of create the peer.