tests/functional: Make sure test case .py files are executable

The top-level test python scripts in tests/functional are supposed to be marked executable; "make check-functional" doesn't care about this, but it allows them to be run as standalone executables to exercise a single test, as docs/devel/testing/functional.rst describes. A couple of files have got into the tree without the executable bit set: fix them. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Thomas Huth <thuth@redhat.com> Message-ID: <20260212151258.1750268-1-peter.maydell@linaro.org> Signed-off-by: Thomas Huth <thuth@redhat.com>