net/http: update bundled SOCKS client

Updates socks_bundle.go to git rev 26e67e7 for:
- 26e67e7 internal/socks: fix socket descriptor leakage in Dialer.Dial

Change-Id: I9ab27a85504d77f1ca2e97cb005f5e37fd3c3ff4
Reviewed-on: https://go-review.googlesource.com/c/147717
Run-TryBot: Mikio Hara <mikioh.public.networking@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/net/http/socks_bundle.go

@@ -380,6 +380,7 @@ func (d *socksDialer) Dial(network, address string) (net.Conn, error) {
 		return nil, &net.OpError{Op: d.cmd.String(), Net: network, Source: proxy, Addr: dst, Err: err}
 	}
 	if _, err := d.DialWithConn(context.Background(), c, network, address); err != nil {
+		c.Close()
 		return nil, err
 	}
 	return c, nil