tests: acpi: do not skip tests when IASL is not installed

tests: acpi: do not skip tests when IASL is not installed

tests do binary comparision so we can check tables without
IASL. Move IASL condition right before decompilation step
and skip it if IASL is not installed.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20190708092410.11167-3-imammedo@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>