Valgrind: Disable flaky CloudPrintURLFetcherBasicTest.

BUG=308309
NOTRY=true
TBR=groby

Review URL: https://codereview.chromium.org/29263009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229506 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229506