plugins: reset textures at negotiation/shutdown
plugins: reset textures at negotiation/shutdown

When caps reconfiguration is called, the new downstream frame size might be
different. Thus, if the downstream caps change,the display's texture map is
reset.

In addition, during pipeline shutdown, textures in texture map have to be
released, since each one have a reference to the GstVaapiDisplay object, which
is a dangerous circular reference.

https://bugzilla.gnome.org/show_bug.cgi?id=769293

Signed-off-by: Víctor Manuel Jáquez Leal <4955886a7d0bd82ff6afce9ed1e93fbb85ab8088@intel.com>

ceyusa/gstreamer-vaapi,ceyusa/gstreamer-vaapi,GStreamer/gstreamer-vaapi,GStreamer/gstreamer-vaapi