tls,http2: handle writes after SSL destroy more gracefully

This might otherwise result in a hard crash when trying
to write to a socket after a sudden disconnect.

Note that the test here uses an aborted `h2load` run to create
the failing requests; That’s far from ideal, but it provides
a reasonably reliably reproduction at this point.

PR-URL: https://github.com/nodejs/node/pull/18987
Fixes: https://github.com/nodejs/node/issues/18973


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>