server: Remove unused query chan and handler.

This removes the query channel and associated handler and plumbing now
that it is no longer used.

This completes the overall effort to convert all of the code related to
updating and querying the server's peer state to synchronous code that
makes use of a separate mutex to protect it.

server.go

@@ -554,7 +554,6 @@ type server struct {
 	modifyRebroadcastInv chan interface{}
 	peerState            peerState
 	banPeers             chan *serverPeer
-	query                chan interface{}
 	relayInv             chan relayMsg
 	broadcast            chan broadcastMsg
 	nat                  *upnpNAT
@@ -2088,11 +2087,6 @@ func (s *server) handleBroadcastMsg(state *peerState, bmsg *broadcastMsg) {
 	})
 }
 
-// handleQuery is the central handler for all queries and commands from other
-// goroutines related to peer state.
-func (s *server) handleQuery(ctx context.Context, state *peerState, querymsg interface{}) {
-}
-
 // disconnectPeer attempts to drop the connection of a targeted peer in the
 // passed peer list. Targets are identified via usage of the passed
 // `compareFunc`, which should return `true` if the passed peer is the target
@@ -2242,9 +2236,6 @@ out:
 		case bmsg := <-s.broadcast:
 			s.handleBroadcastMsg(&s.peerState, &bmsg)
 
-		case qmsg := <-s.query:
-			s.handleQuery(ctx, &s.peerState, qmsg)
-
 		case <-ctx.Done():
 			close(s.quit)
 
@@ -3722,7 +3713,6 @@ func newServer(ctx context.Context, listenAddrs []string, db database.DB,
 		addrManager:          amgr,
 		peerState:            makePeerState(),
 		banPeers:             make(chan *serverPeer, cfg.MaxPeers),
-		query:                make(chan interface{}),
 		relayInv:             make(chan relayMsg, cfg.MaxPeers),
 		broadcast:            make(chan broadcastMsg, cfg.MaxPeers),
 		modifyRebroadcastInv: make(chan interface{}),