fix use before assignment case
fix use before assignment case

Summary: If retries is 0, then `0 < 0` is false, meaning we will skip the `while` loop completely and just try to read retcode, which was never assigned.

Reviewed By: fanzeyi

Differential Revision: D23999523

fbshipit-source-id: fac4a1104eba3585fb52fc8d83163cb1a87b8fee

facebook/wangle,facebook/wangle,facebook/wangle