run-tests: don't print results in unittest mode

A subsequent patch will have unittest print tests for us. Don't perform
old-style printing when in unittest mode.

tests/run-tests.py

@@ -1315,6 +1315,9 b' class TestRunner(object):'
             tests = [self._gettest(t, i, asunit=self.options.unittest)
                      for i, t in enumerate(tests)]
 
+            failed = False
+            warned = False
+
             if self.options.unittest:
                 suite = TestSuite(self, tests=tests)
                 verbosity = 1