Update default image name for alluxio runtime

[cheyang]

Signed-off-by: cheyang [email protected]

Ⅰ. Describe what this PR does

Ⅱ. Does this pull request fix one issue?

fixes #XXXX

Ⅲ. List the added test cases (unit test/integration test) if any, please explain if no tests are needed.

Ⅳ. Describe how to verify it

Ⅴ. Special notes for reviews

[fluid-e2e-bot[bot]]

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