bpo-37658: Fix asyncio.wait_for() to respect waited task status (GH-21894) (GH-21964)

Currently, if `asyncio.wait_for()` itself is cancelled it will always
raise `CancelledError` regardless if the underlying task is still
running.  This is similar to a race with the timeout, which is handled
already.
(cherry picked from commit a2118a14627256197bddcf4fcecad4c264c1e39d)

Co-authored-by: Elvis Pranskevichus <elvis@magic.io>
diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py
index 7ecec96..8b05434 100644
--- a/Lib/asyncio/tasks.py
+++ b/Lib/asyncio/tasks.py
@@ -465,9 +465,12 @@
         try:
             await waiter
         except exceptions.CancelledError:
-            fut.remove_done_callback(cb)
-            fut.cancel()
-            raise
+            if fut.done():
+                return fut.result()
+            else:
+                fut.remove_done_callback(cb)
+                fut.cancel()
+                raise
 
         if fut.done():
             return fut.result()