Fix sqlite endpoint when migrating from sqlite to etcd

Support for 'sqlite' as the endpoint was removed in
https://github.com/k3s-io/kine/pull/320 and the constant removed in
https://github.com/k3s-io/kine/pull/325

Signed-off-by: Brad Davidson <brad.davidson@rancher.com>
(cherry picked from commit 0942e6a0c5)
Signed-off-by: Brad Davidson <brad.davidson@rancher.com>

pkg/etcd/etcd.go

@@ -837,7 +837,7 @@ func (e *ETCD) migrateFromSQLite(ctx context.Context) error {
 	defer cancel()
 
 	_, err = endpoint2.Listen(ctx, endpoint2.Config{
-		Endpoint: endpoint2.SQLiteBackend,
+		Endpoint: "sqlite://",
 	})
 	if err != nil {
 		return err