Fix for progressbar styling

Modified the styling for the progressbar as the last fix didn't seem to
work in latest updates of Chrome, where the progressbar in Umbraco 7.1.6 and Chrome Version 37.0.2062.103 m hadn't a full width.

Previously pull requests: https://github.com/umbraco/Umbraco-CMS/pull/420 and https://github.com/umbraco/Umbraco-CMS/pull/456
There are already multiple files of the new view files with inline style to override umb-loader class 1px hight.
And here I needed to override the absolute  position here, so it push down the folder and image thumbs as it do now, when the progressbar is visible. But there could of course be added an additional class with position: relative; margin: 0px -20px; after the umb-loader-wrapper class to override these styling.