Avoid stomping of bulk postdata inside the bulk_edit_posts() loop.

Merge [28113] to the 3.8 branch.

Reverts [27991] which did not fix it for authors and comment/ping status.

props dd32, DrewAPicture.
fixes #27792.

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3.8.3

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Merge remote-tracking branch 'upstream/3.8-branch' into 3.8-branch