Let fetcher fails less from 503 am: 711f5e943f

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

Change-Id: If5a07ab549008590ee33bcd1404b8e1e7f3f6b5f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>