svn commit likes to hang indefinitely whenever the svnserve server forgets
about the client. This changes ensures the commit queue won't be blocked by
this problem.

Add --quiet to the git fetch command but do not capture anymore.


R=petermayo@chromium.org
BUG=


Review URL: https://chromiumcodereview.appspot.com/11358165

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@166725 0039d316-1c4b-4281-b951-d872f2087c98