test(spanner): add deadline exceeded polling to testCreateBackup2

Author: cy-yun

Spanner/tests/System/BackupTest.php

@@ -292,7 +292,19 @@ public function testCreateBackup2()
         $backup = self::$instance->backup(self::$backupId2);
 
         $op = $backup->create(self::$dbName2, $expireTime);
-        $op->pollUntilComplete();
+        $timeout = time() + self::LONG_TIMEOUT_SECONDS;
+        while (time() < $timeout) {
+            try {
+                $op->pollUntilComplete([
+                    'maxPollingDurationSeconds' => $timeout - time()
+                ]);
+                break;
+            } catch (\Google\ApiCore\ApiException $e) {
+                if ($e->getStatus() !== 'DEADLINE_EXCEEDED') {
+                    throw $e;
+                }
+            }
+        }
 
         self::$deletionQueue->add(function () use ($backup) {
             $backup->delete();