ui/vnc: Drop unused vnc_has_job() and vnc_jobs_clear()

The functions vnc_has_job() and vnc_jobs_clear() are
never used; remove them.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Gonglei <arei.gonglei@huawei.com>
Message-id: 1486146260-8092-1-git-send-email-peter.maydell@linaro.org
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>