Improve stability of decisions in MASA metadata reduction in encoder

It was noted as part of MASA metadata conformance tool development and result analysis that the MASA metadata reduction in encoder produces minor differences that cause larger decision differences which end up with unnecessarily large metadata differences at decoder (even though probably inaudible) when using different platforms (tested here Mac debug & release vs. Linux debug). To help with conformance, it would be good to adjust the code to perform with more stability over different platforms.