sleep() is in time, not sys.

BUG=
R=maruel@chromium.org,szager@chromium.org,cmp@chromium.org

Review URL: https://codereview.chromium.org/34483004

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@230108 0039d316-1c4b-4281-b951-d872f2087c98