We'd like the first bit of early_data and the ClientHello to go in the
same TCP packet if at all possible to enable things like TCP Fast Open.
Also, if you're only going to send one block of early data then you also
don't need to worry about TCP_NODELAY.

Fixes #4783
Reviewed-by: NRichard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4802)