Captive Core's run-from implementation doesn't work for ledgers < 63

[2opremio]

As part of #3153 I found out that run-from doesn't work for ledgers < 63. This is the error I am getting:

time="2020-10-23T10:08:46.126Z" level=error msg="Error in ingestion state machine" current_state="resume(latestSuccessfullyProcessedLedger=1)" error="error preparing range: opening subprocess: error calculating ledger and hash for stelar-core run: error trying to read ledger header 1 from HAS: error opening ledger stream: Bad HTTP response '404 File not found' for GET 'http://localhost:1570/ledger/00/00/00/ledger-00000001.xdr.gz'" next_state=start pid=194 service=ingest

Requesting ledger/00/00/00/ledger-00000001.xdr.gz isn't correct since it's not a checkpoint ledger.

[abuiles]

@2opremio this PR allows online mode to start from ledgers < 63 #3160

[2opremio]

This is partly fixed by #3156 . It still doesn't work for ledger 1, but #3157 is already covering it. Closing