[Linaro-validation] URL Mapping Support

LAVA has support for remapping urls when fetching test images, using a regular expression to match the url and rewrite it. The maps are configured in a file called 'urlmapping.txt' which is usually placed in the dispatcher config directory.

As this was a seemingly undocumented feature, and we no longer need this functionality in the LAVA Lab, I am proposing to remove it. If you are using this code in your LAVA deployment please let me know.

Thanks, Matt Hart