tls_legacy: do not read on OpenSSL's stack
Do not attempt to read data from the socket whilst on OpenSSL's stack, weird things may happen, and this is most likely going to result in some kind of error.
R=@trevnorris
Let's land this change anyway, so it will be easier to work on our AsyncWrap stuff.
Not really going to introduce a test here, because this thing will fail once https://github.com/nodejs/node/pull/4509 or any similar PR will land.