FIX try to get reliable fd number on windows

Author: tomMoral

tests/test_resource_tracker.py

@@ -25,7 +25,11 @@ def _resource_unlink(name, rtype):
 
 def get_rtracker_fd():
     resource_tracker.ensure_running()
-    return resource_tracker._resource_tracker._fd
+    fd = resource_tracker._resource_tracker._fd
+    if sys.platform == "win32":
+        import msvcrt
+        fd = msvcrt.get_osfhandle(fd)
+    return fd
 
 
 class TestResourceTracker: