Add JUnit XML reports; refactor test reporting

* Add Junit output file support
* Differentiate between an expected failure test and an error in the
test, as described in JUnit.
* In case of an error/exception during test, record and attach it to the
Test object and continue running the tests, and show it at the end
during the trial report.

Change-Id: Iedf6d912b3cce3333a187a4ac6d5c6b70fe9d5c5
diff --git a/selftest/trial_test.ok b/selftest/trial_test.ok
index 6ad39a9..7434a10 100644
--- a/selftest/trial_test.ok
+++ b/selftest/trial_test.ok
@@ -4,7 +4,7 @@
 [TMP]/third
 - fetch trial dirs in order
 first
-['taken']
+['last_run', 'run.[TIMESTAMP]', 'taken']
 second
 third
 - no more trial dirs left