getRestoreUrl now uses caas restore api

src/storage/s3.js

@@ -90,6 +90,8 @@ function getRestoreUrl(apiConfig, filename, callback) {
     assert.strictEqual(typeof filename, 'string');
     assert.strictEqual(typeof callback, 'function');
 
+    if (!apiConfig.bucket || !apiConfig.prefix) return new Error('Invalid configuration'); // prevent error in s3
+
     getBackupCredentials(apiConfig, function (error, credentials) {
         if (error) return callback(error);