ci/x86: speed up piglit testing

Add python3 packages to speed up piglit run.

• lxml. An accelerated python xml library using libxml2 (http://lxml.de/)
• simplejson. A fast C based implementation of the python json library. (https://simplejson.readthedocs.org/en/latest/)

Signed-off-by: Christian Gmeiner christian.gmeiner@gmail.com