DO NOT MERGE Fix finalizer ordering/double-free issue

Bug: 18289984

If Surface:finalize() happens after HwuiContext:finalize()
it would try to manipulate a destroyed object. However, as
Surface:finalize() always calls HwuiContext:destroy() this
can be fixed by simply getting rid of HwuiContext's finalizer

Change-Id: I7c912214417ab32891b1c58d045c9721e5f01965
(cherry picked from commit c298f9c9)