Some devices have storage but that's is limited enough not to be able
to store all the metadata, but just a fingerprint id.
In such case we also need to use the local storage to be able to verify.
Fprintd does this already, but we don't do it in the libfprint examples.
So, in in case we enroll, always save the print information to the disk,
while in case we verify we try to load the print from disk and we use
that in case its private data matches the one provided by the device.
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