Don't enforce allowed_hosts for custom_deps.

BUG=430123
R=iannucci@chromium.org,agable@chromium.org

Review URL: https://codereview.chromium.org/701893002

git-svn-id: http://src.chromium.org/chrome/trunk/tools/depot_tools@292853 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
Added transient 502 errors to 'git_retry' list.

BUG=chromium:430343
TEST=None

Review URL: https://codereview.chromium.org/701843004

git-svn-id: http://src.chromium.org/chrome/trunk/tools/depot_tools@292868 4ff67af0-8c30-449e-8e8b-ad334ec8d88c