Fix hClose002 with the threaded RTS IO manager

If 'close fd' failed, then the MVars in the callbackTables would be
left empty, which caused deadlocks when we tried to 'take' them again.

Now we use 'finally' to ensure that they are refilled even if 'close'
throws an exception.

GHC/Event/Thread.hs

@@ -103,8 +103,7 @@ closeFdWith close fd = do
                       (\mgr table -> M.closeFd_ mgr table fd)
                       mgrs
                       tables
-    close fd
-    zipWithM_ finish mgrs tableAndCbApps
+    close fd `finally` zipWithM_ finish mgrs tableAndCbApps
   where
     finish mgr (table', cbApp) = do
       putMVar (M.callbackTableVar mgr fd) table'