Disabling failing WebRTC video tests on Linux.

As sheriff I had to disable some WebRTC tests to cycle the tree green again. 

http://chromegw.corp.google.com/i/internal.chromium.webrtc/waterfall?builder=Linux%20Hideout%20Tester

BUG=281268
TBR=tommi

Review URL: https://codereview.chromium.org/98693002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238071 0039d316-1c4b-4281-b951-d872f2087c98