Don't retry when etag is undefined because the page doesn't exist
Follow-up to 5d1a67757a2dec81d7199ba9a2575015b39acf95.
Bug: T233320
Change-Id: Ice27187862dde75c69bbdb666c0981fce94249ba
(cherry picked from commit f3dfd98e55817c92c29768298d1780f43a901845)