Make the `show_post_locked_dialog` filter hide both the post locked and post taken over dialogs

props azaozz, DH-Shredder. Fixes #24830 for 3.6.


git-svn-id: https://core.svn.wordpress.org/branches/3.6@24886 1a063a9b-81f0-0310-95a4-ce76da25c4cd