Inconsistet use of "connected" field

[skorokhod]

Struct field raft_server_private_t.connected is set in the only place into RAFT_NODE_STATUS_CONNECTED state. But this field is compared in the other place with the const RAFT_NODE_STATUS_DISCONNECTING.
Moreover, connection enum has 2 more states.
So, I suppose that there's some missed functionality which is set RAFT_NODE_STATUS_DISCONNECTING and RAFT_NODE_STATUS_CONNECTING values.