clients: Fix shell background image setting.

If weston.ini is not setting background-image path, then desktop-shell sets ${DATDIR}/weston/pattern.png as background. However in this case width and height is set to 1 during background config and is being scaled to avoid allocation of buffer.

This behavior is not right. Along with background-image path, we should also check if background-color is set. If background color is set, then only scale 1x1 buffer.

This would allow to set pattern.png as default wallpaper of weston correctly, if background-color is also not set in weston.ini file.

Fixes: 3623e46d Signed-off-by: Tanmay Shah tanmay@codeaurora.org