tls: renegotiate should take care of its own state

In the initial version of this test there were two zero-length writes to
force tls state to cycle. The second is not necessary, at least not now,
but the first was. The renegotiate() API should ensure that packet
exchange takes place, not its users, so move the zero-length write into
tls.

See: https://github.com/nodejs/node/pull/14239
See: https://github.com/nodejs/node/commit/b1909d3a70f9

Backport-PR-URL: https://github.com/nodejs/node/pull/27938
PR-URL: https://github.com/nodejs/node/pull/25997


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>