Copy local files should support hdfs semantics

[lubo212]

What changes are proposed in this pull request?

copy local files should support hdfs semantics

Why are the changes needed?

If there is such a local path that needs to be uploaded：

I think users want to see something like this after executing the cp command：

If I upload an empty directory, I want it to be allowed：

[alluxio-bot]

Automated checks report:

• PR title follows the conventions: FAIL
  • The title of the PR does not pass all the checks. Please fix the following issues:
    • First word must be capitalized
• Commits associated with Github account: FAIL
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    Once the author email address has been updated, update the pull request by running:

    git push --force https://github.com/lubo212/alluxio.git localCopySupportHdfs

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[alluxio-bot]

Automated checks report:

• PR title follows the conventions: PASS
• Commits associated with Github account: PASS

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