Make rasterize callback as unique_ptr

When Rasterize callback register into VectorAnimationManager, and
visual was destroyed, the callback base memory might not be deleted.

To avoid this case, let we make the callback's ownership as
VectorAnimationManager.

Change-Id: Ia2d09856e989ac29f8c39cd5cabb2af29d1ed80d
Signed-off-by: Eunki, Hong <eunkiki.hong@samsung.com>