sshpeer: use the doublepipe object for the server to client channel

This restores real-time output from ssh server while waiting for protocol data
sent by the server.

mercurial/sshpeer.py

@@ -160,6 +160,7 b' class sshpeer(wireproto.wirepeer):'
         self.pipeo, self.pipei, self.pipee, self.subprocess = sub
 
         self.pipei = util.bufferedinputpipe(self.pipei)
+        self.pipei = doublepipe(self.ui, self.pipei, self.pipee)
 
         # skip any noise generated by remote shell
         self._callstream("hello")

tests/test-ssh.t

@@ -396,8 +396,8 b' Test hg-ssh in read-only mode:'
   $ hg push --ssh "sh ../ssh.sh"
   pushing to ssh://user@dummy/*/remote (glob)
   searching for changes
+  remote: Permission denied
   abort: pretxnopen.hg-ssh hook failed
-  remote: Permission denied
   [255]
 
   $ cd ..