sshpeer: also use doublepipe for client to server communication
This will allow even more real time output when the server issue output in the
middle a stream push.
#require test-repo pyflakes
$ cd "`dirname "$TESTDIR"`"
run pyflakes on all tracked files ending in .py or without a file ending
(skipping binary file random-seed)
$ hg locate 'set:**.py or grep("^!#.*python")' 2>/dev/null \
> | xargs pyflakes 2>/dev/null | "$TESTDIR/filterpyflakes.py"
tests/filterpyflakes.py:58: undefined name 'undefinedname'