EXT-8285 FIXED prevented wrong handling in accordion of the "scrollToShowRect" event from the child accordion tab's scroll container.

This problem begins from expanding accordion_tab:

1. adjustToFitScreen - calls adjustContainerPanel with "fit screen" rectangle (calls reshape() and resize()).
   Enter adjustContainerPanel("fit screen")
2. reshape calls ensureSelectedVisible -> scrollToShowRect...
   scrollToShowRect notifyParent about "scrollToShowRect" (notifiParent is sync call)
   Enter LLAccordionCtrl::notifyParent("scrollToShowRect")
4. AccordionCtrl handles "scrollToShowRect" notification and perform adjustContainerPanel with "another" rectangle.
   Perform adjustContainerPanel("another") // At least I have not seen 3rd recursive call of adjustContainerPanel
5. Exit LLAccordionCtrl::notifyParent("scrollToShowRect")
6. Exit reshape("fit screen").
7. setRect("fit screen").
8. Exit adjustContainerPanel("fit screen").
...
As result we get AccordionTab that reshaped to "another" rectangle and resized to "fit screen" rectangle.

+ Fixed by handling "scrollToShowRect" message in LLAccordionCtrlTab from "LLScrollContainer".

+ Removed the workaround comment.

Reviewed by Neal Orman at https://codereview.productengine.com/secondlife/r/727/

--HG--
branch : product-engine