Use the revisioned post format metadata when previewing.

fixes #23539. props kovshenin.

git-svn-id: http://core.svn.wordpress.org/trunk@23862 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Gallery is a no-UI post format.

git-svn-id: http://core.svn.wordpress.org/trunk@23863 1a063a9b-81f0-0310-95a4-ce76da25c4cd