daemon: configureLocalContentStore: use FreelistMapType for bolt db

From the [DB.FreelistType] GoDoc:

    // FreelistType sets the backend freelist type. There are two options. Array which is simple but endures
    // dramatic performance degradation if database is large and fragmentation in freelist is common.
    // The alternative one is using hashmap, it is faster in almost all circumstances
    // but it doesn't guarantee that it offers the smallest page id available. In normal case it is safe.
    // The default type is array
    FreelistType FreelistType

While the default is still `FreelistArrayType`, the package shows that
the intent is to make `FreelistMapType` the default in future;
https://pkg.go.dev/go.etcd.io/bbolt@v1.5.0#pkg-constants

    // TODO(ahrtr): eventually we should (step by step)
    //  1. default to `FreelistMapType`;
    //  2. remove the `FreelistArrayType`, do not export `FreelistMapType`
    //     and remove field `FreelistType' from both `DB` and `Options`;

[DB.FreelistType]: https://pkg.go.dev/go.etcd.io/bbolt@v1.5.0#DB.FreelistType

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

daemon/content.go

@@ -20,7 +20,9 @@ func (daemon *Daemon) configureLocalContentStore(ns string) (*namespacedContent,
 	if err := os.MkdirAll(filepath.Join(daemon.root, "content"), 0o700); err != nil {
 		return nil, nil, errors.Wrap(err, "error creating dir for content store")
 	}
-	db, err := bolt.Open(filepath.Join(daemon.root, "content", "metadata.db"), 0o600, nil)
+	db, err := bolt.Open(filepath.Join(daemon.root, "content", "metadata.db"), 0o600, &bolt.Options{
+		FreelistType: bolt.FreelistMapType,
+	})
 	if err != nil {
 		return nil, nil, errors.Wrap(err, "error opening bolt db for content metadata store")
 	}