Some minor improvements, but biggest for here is ErrPipeListenerClosed
is no longer an errors.New where the string matches the text of the now
exported net.ErrClosed in the stdlib, but is just assigned to net.ErrClosed
directly. This should allow us to get rid of the string check for "use of closed
network connection" here now..
Signed-off-by: Daniel Canter <dcanter@microsoft.com>
