gs should retry on SSL handshake timeout

BUG=chromium:657278
TEST=unittest

Change-Id: Idfdb3c49428641d906d377fc3f6861e437f544ef
Reviewed-on: https://chromium-review.googlesource.com/400622
Commit-Ready: Dan Shi <dshi@google.com>
Tested-by: Luigi Semenzato <semenzato@chromium.org>
Reviewed-by: Luigi Semenzato <semenzato@chromium.org>
(cherry picked from commit 5bdabc4cd926d2748b6413e3c4c398150b6fd01d)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2348399
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
2 files changed