gpg: Fix wrong Tofu DB consistency check.
* g10/tofu.c (build_conflict_set): Do not assume MAX_FINGERPRINT_LEN is the size of the fingerprint.
This problem was exhibited by
commit ecbbafb88d920e713439b6b1b8e1b41a6f8d0e38.
- Signed-off-by: Werner Koch <wk@gnupg.org>