BUG-650: use weakCompareAndSwap()

The weak version is documented to be sufficient for statistics and does
not have happens-before effects.

Change-Id: Ic71ff280e8fe166ff4d9def7800be1ad8d1318cd
Signed-off-by: Robert Varga <rovarga@cisco.com>
Merge "BUG-650: use weakCompareAndSwap()"