tests, base: Fixed incorrect implementation of StrTest.ToLower test.
tests, base: Fixed incorrect implementation of StrTest.ToLower test.

Change-Id: I96672052f8c9da9d4f61ff0e8eed324032b1afac
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/22123
Reviewed-by: Daniel Carvalho <91779fc734d358d9575ec4910de29bfcbcaf1b22@yahoo.com.br>
Reviewed-by: Jason Lowe-Power <68c46a606457643eab92053c1c05574abb26f861@lowepower.com>
Maintainer: Jason Lowe-Power <68c46a606457643eab92053c1c05574abb26f861@lowepower.com>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>

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