cogl-framebuffer: Remove all dependencies after a flush
cogl-framebuffer: Remove all dependencies after a flush

After a dependent framebuffer is added to a framebuffer it was never
getting removed. Once the journal for a framebuffer is flushed we no
longer depend on any framebuffers so the list should be cleared. This
was causing leaks of offscreens and textures.

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