doesn't handle connection close about go9p HOT 4 CLOSED

After some debugging I found out that the file.Read call returns correcty an 
EOF error, but my client doesn't return because it's blocked on "defer 
file.Close()".

I believe it's a bug and that file.Close() should be able to complete also in 
this circumstance.

So basically what happens is that after a connection is broken every next 
attempt to send rpc messages will block.

This happens because the "Send" goroutine exits without closing his acceptor 
channel:

func (clnt *Clnt) send() {
    for {
        select {
        case <-clnt.done:
            return
...

Attaching a patch.

Thanks for catching this.

I think there is much simpler fix, just pushed it. Can you please check if it 
fixes the bug for you?

Thanks,
    Lucho