wayland: Disconnect the display when the renderer disconnects
wayland: Disconnect the display when the renderer disconnects

If we don't do this then it might leak connections to the display if
multiple different renderers are tried.

Reviewed-by: Robert Bragg <robert@linux.intel.com>

(cherry picked from commit 8e5b4d40a4d960d0d20927d30ee68a37387fe776)

Distrotech/cogl,Distrotech/cogl,Distrotech/cogl,Distrotech/cogl