647138c coreos-download: add url parameter `stream`

Authored and Committed by abai 17 days ago
    coreos-download: add url parameter `stream`
    
    Adds url parameter `stream` to specify which stream to
    display.
    
    Usage:
     - http://localhost:5000/en/coreos/download?stream=stable
     - http://localhost:5000/en/coreos/download?stream=testing
    
    Signed-off-by: Allen Bai <abai@redhat.com>