EXT-7106 FIX Change from commit callback to validate callback, remove some cyclic tab panel switches.

Problem was caused by incorrect use on Commit callback (which didn't actually prevent from tab switching) which leads to cyclic tab switching.
Validate callback actually prevents tab switching.

Reviwed by Vadim Savchuk at https://codereview.productengine.com/secondlife/r/385/

--HG--
branch : product-engine