Add more asset retries for failing test (GoogleCloudPlatform#976)

Author: bshaffer

asset/test/assetTest.php

@@ -73,6 +73,6 @@ public function testBatchGetAssetsHistory()
             ]);
 
             $this->assertContains($assetName, $output);
-        });
+        }, 10, true);
     }
 }