ssh: fix flaky TestInvalidServerMessage

When shutting down the test, we sometimes see EOF on the server's side
of the connection and sometimes ECONNRESET. In the latter case, based
on timing, it was possible that the server loop would hit Errorf during
shutdown and cause the test to fail.

R=dave
CC=golang-dev
https://golang.org/cl/6125047

ssh/session_test.go

@@ -9,6 +9,7 @@ package ssh
 import (
 	"bytes"
 	"io"
+	"net"
 	"testing"
 
 	"code.google.com/p/go.crypto/ssh/terminal"
@@ -45,6 +46,10 @@ func dial(handler serverType, t *testing.T) *ClientConn {
 			if err == io.EOF {
 				return
 			}
+			// We sometimes get ECONNRESET rather than EOF.
+			if _, ok := err.(*net.OpError); ok {
+				return
+			}
 			if err != nil {
 				t.Errorf("Unable to accept incoming channel request: %v", err)
 				return