config: use a single global macaroon database, scope macaroons in datadir

This commit modifies the way that we create the macaroon database, and
also create the initial macaroons themselves. Rather than creating a
new macaroon DB for each chain, we instead create a single instance for
all chains. Additionally, if the datadir has been modified, and the
macaroon paths haven’t been modified, the macaroons are now scoped to
those paths.

config.go

@@ -38,6 +38,7 @@ const (
 )
 
 var (
+	// TODO(roasbeef): base off of datadir instead?
 	lndHomeDir          = btcutil.AppDataDir("lnd", false)
 	defaultConfigFile   = filepath.Join(lndHomeDir, defaultConfigFilename)
 	defaultDataDir      = filepath.Join(lndHomeDir, defaultDataDirname)
@@ -310,6 +311,21 @@ func loadConfig() (*config, error) {
 		}
 	}
 
+	// At this point, we'll save the base data directory in order to ensure
+	// we don't store the macaroon database within any of the chain
+	// namespaced directories.
+	macaroonDatabaseDir = cfg.DataDir
+
+	// If a custom macaroon directory wasn't specified and the data
+	// directory has changed from the default path, then we'll also update
+	// the path for the macaroons to be generated.
+	if cfg.DataDir != defaultDataDir && cfg.AdminMacPath == defaultAdminMacPath {
+		cfg.AdminMacPath = filepath.Join(cfg.DataDir, defaultAdminMacFilename)
+	}
+	if cfg.DataDir != defaultDataDir && cfg.ReadMacPath == defaultReadMacPath {
+		cfg.ReadMacPath = filepath.Join(cfg.DataDir, defaultReadMacFilename)
+	}
+
 	// Append the network type to the data directory so it is "namespaced"
 	// per network. In addition to the block database, there are other
 	// pieces of data that are saved to disk such as address manager state.