DJ `filepath` inconsistent handling of read/write of `location` with leading slash on S3 protocol

[ttngu207]

Example store config:
{
"protocol": "s3",
"endpoint": "s3.amazonaws.com",
"access_key": "--------------------------",
"secret_key": "--------------------------",
"bucket": "report_bucket",
"location": "/data/report",
"stage": "F:/data/report"
}

On S3, upon insert, the path got written will be something like report_bucket//data/report/... (keeping the leading slash from location).
But when fetching, the leading slash got stripped and the path DJ would search for is actually something like report_bucket/data/report/...