p2p: simplify checkpoint handling

There is no need to select on srv.quit for both ends of the checkpoint channel.

p2p/server.go

@@ -731,11 +731,8 @@ running:
 				c.flags |= trustedConn
 			}
 			// TODO: track in-progress inbound node IDs (pre-Peer) to avoid dialing them.
-			select {
+			c.cont <- srv.postHandshakeChecks(peers, inboundCount, c)
-			case c.cont <- srv.postHandshakeChecks(peers, inboundCount, c):
+
-			case <-srv.quit:
-				break running
-			}
 		case c := <-srv.checkpointAddPeer:
 			// At this point the connection is past the protocol handshake.
 			// Its capabilities are known and the remote identity is verified.
@@ -759,11 +756,7 @@ running:
 			// The dialer logic relies on the assumption that
 			// dial tasks complete after the peer has been added or
 			// discarded. Unblock the task last.
-			select {
+			c.cont <- err
-			case c.cont <- err:
-			case <-srv.quit:
-				break running
-			}
 
 		case pd := <-srv.delpeer:
 			// A peer disconnected.
@@ -1012,12 +1005,7 @@ func (srv *Server) checkpoint(c *conn, stage chan<- *conn) error {
 	case <-srv.quit:
 		return errServerStopped
 	}
-	select {
+	return <-c.cont
-	case err := <-c.cont:
-		return err
-	case <-srv.quit:
-		return errServerStopped
-	}
 }
 
 // runPeer runs in its own goroutine for each peer.