libfido2-util: Refactor pre-flight failure handling

libfido2-util: Refactor pre-flight failure handling

`fido2_is_cred_in_specific_token()` should simply not return error codes
for non-fatal errors. For example, `-ENODEV` can be safely translated to
a `false` return value. When the pre-flight request is not supported, we
should simply return true to instruct the caller to attempt to use the
device anyway.

All error codes returned by the funtion should now be fatal and logged
at error level. Non-fatal errors should only appear in debug logs.