Call visitor_input_teardown() from visitor_input_test_init(), so you
don't have to call it from the actual tests.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <1488544368-30622-22-git-send-email-armbru@redhat.com>