lnrpc+macaroon: skip subserver macaroons on stateless_init

This will prevent the subservers from writing macaroons to disk
when the stateless_init flag is set to true. It accomplishes
this by storing the StatelessInit value in the Macaroon Service.

lnrpc/chainrpc/chainnotifier_server.go

@@ -72,16 +72,6 @@ var (
 		"still in the process of starting")
 )
 
-// fileExists reports whether the named file or directory exists.
-func fileExists(name string) bool {
-	if _, err := os.Stat(name); err != nil {
-		if os.IsNotExist(err) {
-			return false
-		}
-	}
-	return true
-}
-
 // Server is a sub-server of the main RPC server: the chain notifier RPC. This
 // RPC sub-server allows external callers to access the full chain notifier
 // capabilities of lnd. This allows callers to create custom protocols, external
@@ -111,9 +101,12 @@ func New(cfg *Config) (*Server, lnrpc.MacaroonPerms, error) {
 	}
 
 	// Now that we know the full path of the chain notifier macaroon, we can
-	// check to see if we need to create it or not.
+	// check to see if we need to create it or not. If stateless_init is set
+	// then we don't write the macaroons.
 	macFilePath := cfg.ChainNotifierMacPath
-	if cfg.MacService != nil && !fileExists(macFilePath) {
+	if cfg.MacService != nil && !cfg.MacService.StatelessInit &&
+		!lnrpc.FileExists(macFilePath) {
+
 		log.Infof("Baking macaroons for ChainNotifier RPC Server at: %v",
 			macFilePath)
 
@@ -121,8 +114,7 @@ func New(cfg *Config) (*Server, lnrpc.MacaroonPerms, error) {
 		// doesn't yet, exist, so we need to create it with the help of
 		// the main macaroon service.
 		chainNotifierMac, err := cfg.MacService.NewMacaroon(
-			context.Background(),
-			macaroons.DefaultRootKeyID,
+			context.Background(), macaroons.DefaultRootKeyID,
 			macaroonOps...,
 		)
 		if err != nil {
@@ -134,7 +126,7 @@ func New(cfg *Config) (*Server, lnrpc.MacaroonPerms, error) {
 		}
 		err = ioutil.WriteFile(macFilePath, chainNotifierMacBytes, 0644)
 		if err != nil {
-			os.Remove(macFilePath)
+			_ = os.Remove(macFilePath)
 			return nil, nil, err
 		}
 	}