Fix Bug 989463 - Some videos on the video CDN stop working until cache is purged

Update the CDN hostname to fix the playback issue.
Bug 947992 - Request to Verify YouTube on Mozilla.org

Looks like the code has been updated after #1829 is merged. Try again.
Merge pull request #1850 from kyoshino/bug-989463-videos-cdn

Fix Bug 989463 - Some videos on the video CDN stop working until cache is purged
Merge pull request #1848 from kyoshino/bug-947992-youtube-verification

Bug 947992 - Request to Verify YouTube on Mozilla.org