test: runner should return 0 on flaky tests

Make the test runner return a 0 exit code when only
flaky tests fail and --flaky-tests=dontcare is specified.

Ported from a9b642cf5b

PR-URL: https://github.com/nodejs/node/pull/2424
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: João Reis <reis@janeasystems.com>
Reviewed-By: Sakthipriyan Vairamani <thechargingvolcano@gmail.com>

tools/test.py

@@ -75,7 +75,9 @@ class ProgressIndicator(object):
     self.remaining = len(cases)
     self.total = len(cases)
     self.failed = [ ]
+    self.flaky_failed = [ ]
     self.crashed = 0
+    self.flaky_crashed = 0
     self.lock = threading.Lock()
     self.shutdown_event = threading.Event()
 
@@ -143,6 +145,11 @@ class ProgressIndicator(object):
         return
       self.lock.acquire()
       if output.UnexpectedOutput():
+        if FLAKY in output.test.outcomes and self.flaky_tests_mode == DONTCARE:
+          self.flaky_failed.append(output)
+          if output.HasCrashed():
+            self.flaky_crashed += 1
+        else:
           self.failed.append(output)
           if output.HasCrashed():
             self.crashed += 1