Fix #36451 : Alla breve forced to 2/2

Fix #36451 : Alla breve forced to 2/2

Basically reverts commit https://github.com/musescore/musescore/commit/7ab8acd which was intended to fix issue http://musescore.org/en/node/14548 (apparently no longer needed)

Fix code is kept but commented out, with detailed comment and a small addition, in case the original issue pops up again in the future.

See http://musescore.org/en/node/36541 for more details, score samples and discussion.