Make default Parallelism in T2TModel reusing (removes "parallel_0" from variable names in colab).

PiperOrigin-RevId: 177265031

Author: Lukasz Kaiser

tensor2tensor/utils/t2t_model.py

@@ -75,7 +75,7 @@ def __init__(self,
     super(T2TModel, self).__init__(
         trainable=mode == tf.estimator.ModeKeys.TRAIN, name=name)
     if data_parallelism is None:
-      data_parallelism = eu.Parallelism([""])
+      data_parallelism = eu.Parallelism([""], reuse=True)
     if ps_devices is None:
       ps_devices = [""]
     if problem_hparams is None: