apply goimports -w to generated files

[jimexist]

fixes #256

No good way to tell whether a file was generated. a better way is to ensure that all files and newly submitted ones are goimported. also from now on I think it is better to enforce that even generated code are pre-goimported.

I didn't fix all the lint warnings because I am afraid of changing any code other than using goimport. I suggest that the original author do the changes instead.

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This change is 

[k8s-ci-robot]

Hi @jimexist. Thanks for your PR.

I'm waiting for a kubernetes or tensorflow member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[coveralls]

Coverage remained the same at 28.518% when pulling 54cdeff on Jimexist:fix-256 into ed7cae7 on tensorflow:master.

[coveralls]

Coverage decreased (-0.06%) to 28.458% when pulling 04eef00 on Jimexist:fix-256 into ed7cae7 on tensorflow:master.

[zjj2wry]

/ok-to-test

[jlewi]

I think redundant return is to because that's a lint issue in one of the auto copy files. Instead of excluding this warning for all files can we just exclude the deepcopy file from lint checks?

[jimexist]

ok i will try to do a follow up PR

[jlewi]

Thanks. I went ahead and submit this because it fixes the travis build

[jlewi]

Going to merge this so we fix the build.