[patch] Choose URL in build-cloud-images based on new command line argument

[Kushal Das]

Hi,

The attached patch adds a new command line argument to the
build-cloud-images script, if that value is mash then it will use a
different URL else it will use standard URL to build cloud images. I
go the mash URL from the git history as suggested by Dennis.

Note: The patch is not tested.

Kushal
-- 
Fedora Cloud Engineer
CPython Core Developer
http://kushaldas.in