Adds retries for Spanner tests, fixes a few test errors (GoogleCloudPlatform#931)

Author: bshaffer

bigtable/src/create_dev_instance.php

@@ -94,8 +94,7 @@
         );
         $operationResponse->pollUntilComplete();
         if (!$operationResponse->operationSucceeded()) {
-            $error = $operationResponse->getError();
-            throw $error;
+            print('Error: ' . $operationResponse->getError());
         } else {
             printf("Instance %s created.", $instance_id);
         }

bigtable/src/create_production_instance.php

@@ -85,8 +85,7 @@
         );
         $operationResponse->pollUntilComplete();
         if (!$operationResponse->operationSucceeded()) {
-            $error = $operationResponse->getError();
-            throw $error;
+            print('Error: ' . $operationResponse->getError());
         } else {
             printf("Instance %s created.", $instance_id);
         }

spanner/test/spannerTest.php

@@ -61,6 +61,11 @@ public static function setUpBeforeClass()
         self::$instance = $spanner->instance(self::$instanceId);
     }
 
+    public function setUp()
+    {
+        $this->useExpectationFailedBackoff();
+    }
+
     public function testCreateDatabase()
     {
         $output = $this->runCommand('create-database');