Fixed missing run in tf keras elastic mode

[BobLiu20]

Checklist before submitting

• [ yes ] Did you read the contributor guide?
• [ N/A ] Did you update the docs?
• [ N/A ] Did you write any tests to validate this change?
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Description

Can not run examples/elastic/tensorflow_keras_mnist_elastic.py in elastic mode.

Fixes # (issue).

1. missing run decorator in elastic.py file. Just import it and working well now.

Review process to land

1. All tests and other checks must succeed.
2. At least one member of the technical steering committee must review and approve.
3. If any member of the technical steering committee requests changes, they must be addressed.

[tgaddair]

Thanks for the PR, @BobLiu20! Can you add this change to horovod/tensorflow/keras/elastic.py as well?

[BobLiu20]

Thanks for the PR, @BobLiu20! Can you add this change to horovod/tensorflow/keras/elastic.py as well?

Hi @tgaddair . Added it. Thanks.

[tgaddair]

Thanks! Looks good, seems test failures are unrelated, so I'll take a look at those in a separate PR.