pilot+lnd: let autopilot.Manager manage pilot-agent

This commit moves the responsibility of managing the life cycle of the
autopilot from main to the autopilot Manager. It utilizes the recently
introduced autopilot Manager, and just sets up the necessary interfaces
for the Manager to properly set up the required subscriptions when
starting the agent.

lnd.go

@@ -38,6 +38,7 @@ import (
 	proxy "github.com/grpc-ecosystem/grpc-gateway/runtime"
 	flags "github.com/jessevdk/go-flags"
 
+	"github.com/lightningnetwork/lnd/autopilot"
 	"github.com/lightningnetwork/lnd/build"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/keychain"
@@ -312,6 +313,21 @@ func lndMain() error {
 		return err
 	}
 
+	// Set up an auotpilot manager from the current config. This will be
+	// used to manage the underlying autopilot agent, starting and stopping
+	// it at will.
+	atplCfg := initAutoPilot(server, cfg.Autopilot)
+	atplManager, err := autopilot.NewManager(atplCfg)
+	if err != nil {
+		ltndLog.Errorf("unable to create autopilot manager: %v", err)
+		return err
+	}
+	if err := atplManager.Start(); err != nil {
+		ltndLog.Errorf("unable to start autopilot manager: %v", err)
+		return err
+	}
+	defer atplManager.Stop()
+
 	// Initialize, and register our implementation of the gRPC interface
 	// exported by the rpcServer.
 	rpcServer, err := newRPCServer(
@@ -375,20 +391,14 @@ func lndMain() error {
 	defer server.Stop()
 
 	// Now that the server has started, if the autopilot mode is currently
-	// active, then we'll initialize a fresh instance of it and start it.
+	// active, then we'll start the autopilot agent immediately. It will be
+	// stopped together with the autopilot service.
 	if cfg.Autopilot.Active {
-		pilot, err := initAutoPilot(server, cfg.Autopilot)
-		if err != nil {
-			ltndLog.Errorf("unable to create autopilot agent: %v",
-				err)
-			return err
-		}
-		if err := pilot.Start(); err != nil {
+		if err := atplManager.StartAgent(); err != nil {
 			ltndLog.Errorf("unable to start autopilot agent: %v",
 				err)
 			return err
 		}
-		defer pilot.Stop()
 	}
 
 	// Wait for shutdown signal from either a graceful server stop or from