Add an option for maximum retries on all S3 requests

Closes #1877 (closed)

This can make the flood problems mentioned in frontend!1802 (merged) worse, since this affects every single S3 request including those made by RetrieveTask.

Merely shutting down MinIO locally will not trigger the retries because the standard retry mode ignores EndpointConnectionError, so to test locally, you need to mess with Traefik.

Add this to traefik.toml:

[experimental]
  [experimental.plugins]
    [experimental.plugins.noop]
      moduleName = "github.com/traefik-contrib/noop"
      version = "v0.1.0"

Then add those labels in docker/docker-compose.services.yml:

services:
  # ...
  minio:
    # ...
    labels:
      # ...
      traefik.http.routers.minio.middlewares: gandalf
      traefik.http.middlewares.gandalf.plugin.noop.responseCode: 502

Now accessing MinIO always returns HTTP 502 and Boto will keep retrying.