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.


R=maruel@chromium.org
BUG=


Review URL: https://chromiumcodereview.appspot.com/12440058

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@189382 0039d316-1c4b-4281-b951-d872f2087c98