Add a slight improvement of the Coccinelle semantic patch from commit
007b06578a, and use it to clean up. It leaves dead Error * variables
behind, cleaned up manually.
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Alexander Graf <agraf@suse.de>
Cc: Eric Blake <eblake@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Message-Id: <20181017082702.5581-3-armbru@redhat.com>