ds001510: files download as MD5E checksum rather than correct file name

[jbwexler]

This occurs when downloading from gui https://openneuro.org/datasets/ds001510/versions/2.0.2. Example: sub-15_task-perception_run-02_bold.nii.gz downloaded as MD5E-s257425408--fc1cacfc5872f06bd96c1cd6682738e9.nii.gz.

[nellh]

This should be fairly temporary for most datasets but the server doesn't actually have a way to know what the filename is in this case. I think we could send it as a hint though to avoid this in the few cases where it is needed (usually when a snapshot is exporting still). I fixed it for this one but I've been gradually clearing the cache for datasets to upgrade to the new URL format without disrupting things too much.