Some of the previous cleanups broke the downloadfilename functionality.
This change fixes the code to ensure the commandline is correctly built.
Thanks Kristof Robot <krirobo@gmail.com> for reporting the issue.
(Bitbake rev: e008d9bb07e5d1a3584cc04ca2cd3dd906fd5759)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>