Add fixed random seed for Emformer RNN-T recipe test (#2220)

Summary:
Adds fixed random seed to Emformer RNN-T training recipe test.

Pull Request resolved: https://github.com/pytorch/audio/pull/2220

Reviewed By: nateanl

Differential Revision: D34180644

Pulled By: hwangjeff

fbshipit-source-id: 2dc364f3f7cd666fa490514ae460538231c097e9

test/torchaudio_unittest/example/emformer_rnnt/test_librispeech_lightning.py

@@ -78,6 +78,10 @@ def get_lightning_module():
 @skipIfNoModule("pytorch_lightning")
 @skipIfNoModule("sentencepiece")
 class TestLibriSpeechRNNTModule(TorchaudioTestCase):
+    @classmethod
+    def setUpClass(cls) -> None:
+        torch.random.manual_seed(31)
+
     def test_training_step(self):
         with get_lightning_module() as lightning_module:
             train_dataloader = lightning_module.train_dataloader()