update height calculating of  dragger with the paddings

My dragger has paddings and in some case the ```mCSB_draggerContainer``` hides my dragger.

And I got the problem like these:
![screenshot 2013-12-03 18 37 14](https://f.cloud.github.com/assets/478100/1667736/ba88ac74-5c5a-11e3-8a1e-98738b21213e.png)

And what I need is some like these:
![screenshot 2013-12-03 18 38 17](https://f.cloud.github.com/assets/478100/1667748/e09fc12c-5c5a-11e3-9683-28c9185bebf0.png)

Thanks