test.c: Fix counting of tests and add 2 new tests

The unit test XML output was counting all registered tests as "run"
even when only a subset were actually requested to be run and
the "failures" attribute was missing.

* The "tests" attribute of the "testsuite" element in the
  output XML now reflects only the tests actually requested
  to be executed instead of all the tests registered.

* The "failures" attribute was added to the "testsuite"
  element.

Also added 2 new unit tests that just pass and fail to be
used for CI testing.

Change-Id: Ia137814b5aeb0e1a44c75034bd3615c26021da69
(cherry picked from commit a0fd95ef52593e4b7471d8045683f81b101d014a)