channel: Do not return error if the server closed the channel

If the server properly closed the channel, the client should not return
error if it finds the channel closed.

Fixes T231

Signed-off-by: Anderson Toshiyuki Sasaki <ansasaki@redhat.com>
Reviewed-by: Jakub Jelen <jjelen@redhat.com>
(cherry picked from commit 750e4f3f9d3ec879929801d65a500ec3ad84ff67)