Let fetcher fails less from 503 am: 711f5e943f am: b8c38af9bc

Original change: https://android-review.googlesource.com/c/platform/tools/treble/+/2535284

Change-Id: Id6b37ce5e11b9959bb1f6b1caa084a607b0eded0
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>