Change url creation for ocrd fulltext access

Olahd fulltext creation fails currently. Cause is that they cannot be loaded from olahd because the url to fetch it is wrong. My theory why it worked before but doesn't work now is: It works when OLAHDS_FILE_KEY_PATTERN is set to the full URL and not just /export.... But this would make the s3 fail. Then we introduced S3 and had to switch the pattern for OLAHDS_FILE_KEY_PATTERN to make s3 work. But we didn't notice up until now that fulltexts where not created any more