Error accessing dandi-loaded raw files

[samuelbray32]

Issue

• DandiPath typically stores the original raw nwb file rather than the copy file (_.nwb) made by spyglass
• The logic for checking for the original file got moved here by Allow recompute via _make_file func #1093
• Works for streaming the file, but the key on __open_nwb_files is now the original raw file name rather than the copy raw file name
• Creates error when accessing the file late

Soln

• Move the check logic into _open_nwb
• make the key from the copy file path