tests: Updated tests to download from http://dist.gem5.org

tests: Updated tests to download from dist.gem5.org

Previously some tests, and test resources, downloaded content from
http://gem5.org . This is being migrated to http://dist.gem5.org.
http://dist.gem5.org should be used to store and retrieve resources
going forward.

Change-Id: I7162c76b9b8dc07657a6ba50d643fc93c9824fdf
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/24548
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>
Tested-by: kokoro <noreply+kokoro@google.com>