remotefilelog: rework workaround for sshpeer deadlocks

The wrapping of `sshpeer.cleanup` silently broke when `cleanup` was
renamed to `_cleanup`, a couple of years ago.

I don't know what `orig.im_self` is, but regardless, the intention of
the wrapping seems pretty clear: close stderr before
sshpeer._cleanuppipes blocks on it. So do that.

Differential Revision: https://phab.mercurial-scm.org/D9997

hgext/remotefilelog/connectionpool.py

@@ -43,17 +43,19 b' class connectionpool(object):'
 
         if conn is None:
 
-            def _cleanup(orig):
-                # close pipee first so peer.cleanup reading it won't deadlock,
-                # if there are other processes with pipeo open (i.e. us).
-                peer = orig.im_self
-                if util.safehasattr(peer, 'pipee'):
-                    peer.pipee.close()
-                return orig()
+            peer = hg.peer(self._repo.ui, {}, path)
+            if util.safehasattr(peer, '_cleanup'):
 
-            peer = hg.peer(self._repo.ui, {}, path)
-            if util.safehasattr(peer, 'cleanup'):
-                extensions.wrapfunction(peer, b'cleanup', _cleanup)
+                class mypeer(peer.__class__):
+                    def _cleanup(self):
+                        # close pipee first so peer.cleanup reading it won't
+                        # deadlock, if there are other processes with pipeo
+                        # open (i.e. us).
+                        if util.safehasattr(self, 'pipee'):
+                            self.pipee.close()
+                        return super(mypeer, self)._cleanup()
+
+                peer.__class__ = mypeer
 
             conn = connection(pathpool, peer)