TinyMCE: don't show image toolbar for placeholder images. See #30147.

git-svn-id: https://develop.svn.wordpress.org/trunk@30361 602fd350-edb4-49c9-b593-d223f7449a82
Fix typo in [30361], see #30147.

git-svn-id: https://develop.svn.wordpress.org/trunk@30362 602fd350-edb4-49c9-b593-d223f7449a82
TinyMCE: fix the border on the image toolbar arrow. Props afercia, see #30147.

git-svn-id: https://develop.svn.wordpress.org/trunk@30363 602fd350-edb4-49c9-b593-d223f7449a82