gpgv: cleanup statusfd parsing a bit

gpgv: cleanup statusfd parsing a bit

We parse the messages we receive into two big categories: Most of the
messages have a keyid as well as a userid and as they are errors we want
to show the userids as well. The other category is also errors, but have
no userid (like NO_PUBKEY). Explicitly expressing this in code should
make it a bit easier to look at and it also help in dropping additional
fields or just the newline at the end consistently.

Git-Dch: Ignore