[8.5](backport #1951) Fix fleet.migration.total log key overlap

[mergify]

This is an automatic backport of pull request #1951 done by Mergify.

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[elasticmachine]

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• Start Time: 2022-10-06T17:32:29.613+0000

• Duration: 11 min 21 sec

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Test	Results
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Passed	352
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Total	353

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