Media: Account for the most obvious and common style conflicts that may occur...

Media: Account for the most obvious and common style conflicts that may occur when the media modal is loaded on the frontend. Tested primarily with P2. props lessbloat, helenyhou. fixes #22752.



git-svn-id: https://core.svn.wordpress.org/trunk@23077 1a063a9b-81f0-0310-95a4-ce76da25c4cd