fix silly bug in signing key fingerprint calculation for display

This was causing the first byte of the signature to be chopped off, so
therefore it would not validate since the fingerprint of the cert from
the net connection had the right fingerprint, but it was compared to the
stored, truncated version.

This also means that the database version needs to be bumped to trigger an
upgrade so that the bad 62 char fingerprints are removed from the database.