TOFU: Slow list-keys

[Patrick Brunschwig]

I use gpg 2.1.10. I noticed that with TOFU enabled, key listing became
quite slow. My keyring (keybox) contains around 550 public keys.

I run the command: gpg2 --fixed-list-mode --with-fingerprint \
--with-colons --status-fd 2 --list-key

With trust-model pgp: 7 seconds

With trust-model tofu and tofu+pgp: 18 seconds

I'm also seeing lots of "gpg: TOFU: Ignoring revoked user id ... "
output. I believe this should better be debugging output only.

-Patrick