node: fix megacheck warnings

node/config.go

@@ -35,7 +35,7 @@ import (
 	"github.com/ethereum/go-ethereum/p2p/discover"
 )
 
-var (
+const (
 	datadirPrivateKey      = "nodekey"            // Path within the datadir to the node's private key
 	datadirDefaultKeyStore = "keystore"           // Path within the datadir to the keystore
 	datadirStaticNodes     = "static-nodes.json"  // Path within the datadir to the static node list
@@ -160,7 +160,7 @@ func (c *Config) NodeDB() string {
 	if c.DataDir == "" {
 		return "" // ephemeral
 	}
-	return c.resolvePath("nodes")
+	return c.resolvePath(datadirNodeDatabase)
 }
 
 // DefaultIPCEndpoint returns the IPC path used by default.