Remove integer sanitization from ringbuffer pointer arithmetic

The AudioTrackShared ringbuffer uses int32 positions and allows overflow.
This confuses the integer sanitization code and makes it panic.
The simplest solution for now seems to be to remove sanitization
from the methods that touch the ringbuffer pointers.

Bug 27680456

Change-Id: Ie4d7daf0fb1e4e223ee97c412af7b1bd9c6916eb