Skipping SDK update check in AppRTC test.

Turns out a freshly checked out appspot SDK will ask some silly questions. Suppress this.

TBR=xians@chromium.org
BUG=303021

Review URL: https://codereview.chromium.org/27538002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228929 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228929