Add another error code where gclient sync should retry.
Add another error code where gclient sync should retry.

TBR=dpranke@chromium.org
BUG=
TEST=

Review URL: http://codereview.chromium.org/8233033

git-svn-id: bd64dd6fa6f3f0ed0c0666d1018379882b742947@104959 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

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