Matrix decompose scaling bug

@Deltakosh

The matrix decompose returns wrong scale value when scale is negative

see

https://www.babylonjs-playground.com/#ZXZI83

Here scling.z is being set to -2, decompose returns +2

I think the bug got introduced by this change

https://github.com/BabylonJS/Babylon.js/commit/8d1b546a20b3398556f0fe98f6d57329bce92687#diff-ccd6f7b0cc7c001d6fdf41cff591c6a6

Fixed matrix decomposition with negative scaling