aboutToDraw() should be called before checking the painter device,
if no device, aboutToDraw() will create a new one.

Also just release the FBO when delete tile, not need to release the fbo
after each draw.

Change-Id: Ida5954f1c65f25f0ce273f732c1608ed49bc148c
Reviewed-by: Michael Brasser <michael.brasser@nokia.com>