test: add retries to vision tests (GoogleCloudPlatform#1038)

Author: bshaffer

vision/test/visionTest.php

@@ -21,13 +21,17 @@
 use Google\Cloud\TestUtils\TestTrait;
 use Google\Cloud\TestUtils\ExecuteCommandTrait;
 use PHPUnit\Framework\TestCase;
+use PHPUnitRetry\RetryTrait;
 
 /**
  * Unit Tests for vision commands.
+ *
+ * @retryAttempts 2
  */
 class visionTest extends TestCase
 {
     use TestTrait;
+    use RetryTrait;
     use ExecuteCommandTrait;
 
     private static $commandFile = __DIR__ . '/../vision.php';