Though bug description mentioned only appearance, bug reproduced for all slidercontrols. The cause of returning on escape to old value
instead of last commited one was that on commit slidercontrol set text for it's lineeditor which was the same as the one currently typed
into lineeditor(and it seems logical). But LLLineEditor::setText() has check at it's beginning which compares text which is being set to the
one which is already there. If this check succeeds, we exit the method and thus saving of value for revert is not reached. That's why when revert happened
on escape older value then the last commited was set in lineeditor.

- Added additional call of setText() in sliderctrl to force changes in currently set text so that on next call with "real" text saving of reverted value was reached.

Reviewed by Vadim Savchuk at https://codereview.productengine.com/secondlife/r/856/

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branch : product-engine