cogl-texture-2d-sliced: Use the converted bitmap when uploading
cogl-texture-2d-sliced: Use the converted bitmap when uploading

When uploading texture data the cogl-texture-2d-sliced backend was
using _cogl_texture_prepare_for_upload to create a bitmap suitable for
upload but then it was using the original bitmap instead of the new
bitmap for the data. This was causing any format conversions performed
by cogl_texture_prepare_for_upload to be ignored.

http://bugzilla.openedhand.com/show_bug.cgi?id=2059

kerrickstaley/clutter-vala,djdeath/clutter-multithreaded,GNOME/clutter,heysion/clutter-clone,dlespiau/clutter,djdeath/clutter-multithreaded,spatulasnout/clutter,rkudiyarov/clutter_osx,Distrotech/clutter,heysion/clutter-clone,jigpu/clutter,Distrotech/clutter,kerrickstaley/clutter-vala,nobled/clutter,spatulasnout/clutter,djdeath/clutter-android,heysion/clutter-clone,djdeath/clutter-android,spatulasnout/clutter,GNOME/clutter,rkudiyarov/clutter_osx,rkudiyarov/clutter_osx,jigpu/clutter,ebassi/clutter,kerrickstaley/clutter-vala,Distrotech/clutter,collects/clutter,collects/clutter,djdeath/clutter,GNOME/clutter,Distrotech/clutter,djdeath/clutter,Distrotech/clutter,Distrotech/clutter,spatulasnout/clutter,nobled/clutter,djdeath/clutter,djdeath/clutter-android,collects/clutter,dlespiau/clutter,djdeath/clutter-android,GNOME/clutter,djdeath/clutter-multithreaded,collects/clutter,ebassi/clutter,nobled/clutter,djdeath/clutter,heysion/clutter-clone,djdeath/clutter-multithreaded,djdeath/clutter,rkudiyarov/clutter_osx,ebassi/clutter,jigpu/clutter,ebassi/clutter,ebassi/clutter,djdeath/clutter,spatulasnout/clutter,jigpu/clutter,jigpu/clutter,dlespiau/clutter,heysion/clutter-clone,kerrickstaley/clutter-vala,djdeath/clutter-android,collects/clutter,GNOME/clutter,jigpu/clutter