Improve junit xml generated fields

* trial ('testsuites' node): Add fields 'tests', 'errors', 'failures',
  'time'.
* testsuite: Add fields 'errors', 'failures', 'skipped',
  'disabled'
* test: Add field 'classname' (empty).

Fix and improve suite.py and test.py to count errors, skipped, failures
properly.

Change-Id: Ie2d10cee88a9c0d829e4620553164cf3150e8e5c
3 files changed