VerifyHostname is called by tls.Conn during Handshake and does not need to be called explicitly.

Change-Id: I22b7fa137e76bb4be3d0018813a571acfb882219
Reviewed-on: https://go-review.googlesource.com/98618
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>