gst-plugins-bad: opus + jpegformat: unbreak non-debug build

opus + jpegformat plugin builds fail when gstreamer is configured with
--disable-gst-debug as they are checking the GST_DISABLE_DEBUG symbol
instead of GST_DISABLE_GST_DEBUG.

Submitted upstream as https://bugzilla.gnome.org/show_bug.cgi?id=683850



Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>