tests/functional: enable force refresh of cached assets

If the 'QEMU_TEST_REFRESH_CACHE' environment variable is set, then
ignore any existing cached asset and download a fresh copy.

This can be used to selectively refresh assets if set before running
a single test script.

Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20250829142616.2633254-2-berrange@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>
2 files changed