Fix #6: patch sys after thread

from PR #232

gevent/monkey.py

@@ -171,14 +171,16 @@ def patch_all(socket=True, dns=True, time=True, select=True, thread=True, os=Tru
               subprocess=False, sys=False, aggressive=True, Event=False):
     """Do all of the default monkey patching (calls every other function in this module."""
     # order is important
-    if sys:
-        patch_sys()
     if os:
         patch_os()
     if time:
         patch_time()
     if thread:
         patch_thread(Event=Event)
+    # sys must be patched after thread. in other cases threading._shutdown will be
+    # initiated to _MainThread with real thread ident
+    if sys:
+        patch_sys()
     if socket:
         patch_socket(dns=dns, aggressive=aggressive)
     if select: