crypto/tls: fix TestVerifyHostnameResumed

crypto/tls: fix TestVerifyHostnameResumed

In TLS 1.3 session tickets are delivered after the handshake, and it
looks like now the Google servers wait until the first flight of data to
send them (or our timeout is too low). Cause some data to be sent so we
can avoid the guessing game.

Fixes #32090

Change-Id: I54af4acb3a89cc70c9e14a5dfe18a44c29a841a7
Reviewed-on: https://go-review.googlesource.com/c/go/+/177877
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>