gpg: Validate the trustdb after the import of a trusted key.

* g10/import.c (import_one_real): Rename non_self to non_self_or_utk.
If not set after chk_self_sigs check whether the imported key is an
ultimately trusted key.

The revalidation mark was only set if the imported key had a new key
signature. This is in general correct but not if the imported key is
a trusted key.

• GnuPG-bug-id: T7200