GitLab

* fix test benchmark_graph_1_gpu_no_dist_strat failing

- Failure only occurs when all 1_gpu tests are run
together with the error:
tensorflow.python.framework.errors_impl.NotFoundError:
Resource localhost/logdir:/tmp/cifar10_model/
N10tensorflow22SummaryWriterInterfaceE does not exist.
[Op:WriteScalarSummary] name: epoch_loss/

Another fix might be to generate a different model_dir
in the core code, but that has other draw backs such as
restarting from the checkpoint.

* Model_dir for all tests.