Fix the remaining failing test on Python 3.4

zdrun.py gets unhappy if it is spawned with no open file descriptors: it
creates a master socket as fd 1 and then proptly os.dup2's it out of
existence with the transcript pipe.

src/zdaemon/tests/parent.py

@@ -35,10 +35,22 @@ def main():
 def shutup():
     os.close(0)
     sys.stdin = sys.__stdin__ = open("/dev/null")
+    try: # PEP 446, Python >= 3.4
+        os.set_inheritable(sys.stdin.fileno(), True)
+    except AttributeError:
+        pass
     os.close(1)
     sys.stdout = sys.__stdout__ = open("/dev/null", "w")
+    try: # PEP 446, Python >= 3.4
+        os.set_inheritable(sys.stdout.fileno(), True)
+    except AttributeError:
+        pass
     os.close(2)
     sys.stderr = sys.__stderr__ = open("/dev/null", "w")
+    try: # PEP 446, Python >= 3.4
+        os.set_inheritable(sys.stderr.fileno(), True)
+    except AttributeError:
+        pass
 
 if __name__ == '__main__':
     main()