Fix CHECK failure in libosi-allocation-tracker fuzzer

If the allocatior had not been initialized prior to a call to
allocation_tracker_notify_alloc, the function would immediately
return the provided pointer, but not track it (as the tracker is not
initialized). On fuzzer loop teardown, allocation_tracker_notify_free
is called, cannot find the pointer/id pair in its map, and asserts.

Test: Ran compiled fuzzer with crashfile before and after change to
      verify crash had been fixed
      (`./libosi_fuzz_allocation_tracker ./corpus/ -runs=0`)
Signed-off-by: Michael Ensing <michael.ensing@leviathansecurity.com>
Change-Id: I42e2759aa6efb9b6733509e298a552600e874f82