Allow any format for noop backup site

src/backupformats.js

@@ -19,9 +19,12 @@ function api(format) {
     throw new BoxError(BoxError.INTERNAL_ERROR, `Undefined format ${format}`);
 }
 
-function validateFormat(format) {
+function validateFormat(provider, format) {
+    assert.strictEqual(typeof provider, 'string');
     assert.strictEqual(typeof format, 'string');
 
+    if (provider === 'noop') return null;
+
     if (format === 'tgz' || format == 'rsync') return null;
 
     return new BoxError(BoxError.BAD_FIELD, 'Invalid backup format');