reopen logs on USR1 to master

gunicorn/arbiter.py

@@ -248,6 +248,7 @@ class Arbiter(object):
         Kill all workers by sending them a SIGUSR1
         """
         self.kill_workers(signal.SIGUSR1)
+        self.log.reopen_files()
     
     def handle_usr2(self):
         """\