tests can now use 'tenv.test().set_kpis(some_dict)' to set any kind of
data as KPIs, which will be presented in the junit report.
The representation of KPIs in the xml file doesn't follow the junit
format, mainly because it has no support for per-test properties.
Change-Id: I00e976f65a202e82d440bf33708f06c8ce2643e2