test/crypto: add_gnupg_home should have ultimate trust on "its own" key

The typical use case for gpg is that if you control a secret key, you
mark it with "ultimate" ownertrust.

The opaque --import-ownertrust mechanism is GnuPG's standard mechanism
to set up ultimate ownertrust (the ":6:" means "ultimate", for
whatever reason).

We adjust the test suite to match this change, inverting the sense of
one test: since the default is now that the user ID of the suite's own
key is valid, we change the test to make sure that the user ID is not
emitted when it is *not* valid.

Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>