tests/functional: skip vulkan test if missing vulkaninfo

tests/functional: skip vulkan test if missing vulkaninfo

I could have sworn I had this is a previous iteration of the patches
but I guess it got lost in a re-base. As we are going to call
vulkaninfo to probe for "bad" drivers we need to skip if the binary
isn't available.

Fixes: 9f7e493d11 (tests/functional: skip vulkan tests with nVidia)
Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-ID: <20250312190314.1632357-1-alex.bennee@linaro.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>