tests: Fix downloader check
tests: Fix downloader check

This test was failing due to references to a "downloader_dir" variable.
It should be "downloader_directory".

This is responsible for the Weekly test failing:
https://jenkins.gem5.org/job/weekly/55

Change-Id: Ia898726b75be1bfc2b6f49383be750a250c24af0
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/60349
Maintainer: Bobby Bruce <b9dba908ffb6c6d8ffe449cc88b3709c13c485c2@ucdavis.edu>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Reviewed-by: Jason Lowe-Power <92de577f37050ad05b60626d2f17913f40dcb1a2@gmail.com>

gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5,gem5/gem5