Don't attempt to download ledger from S3 when accounts are specified as a list

[georgeee]

In logs from local node testing I found this error in logs:

[%log error]
            "Need S3 hash specified in runtime config to verify download for \
             $ledger (root hash $root_hash), refusing unsafe download"
            ~metadata:
              [ ( "root_hash"
                , `String (Option.value ~default:"not specified" config.hash) )
              ; ("ledger", `String ledger_name_prefix)
              ] ;

Ledger was specified as a list of accounts (in runtime config). I believe we shouldn't be attempting retrieval from S3 at all in case of accounts specified as a list. This confuses node operator when seen.

[deepthiskumar]

This should be the case already? Does the node crash?