Fix ex_data memory leak

Code was added in commit 62f488d3 that overwrite the last ex_data valye
using CRYPTO_dup_ex_data() causing a memory leak and potentially
confusing the ex_data dup() callback.

In ssl_session_dup(), new-up the ex_data before calling
CRYPTO_dup_ex_data(); all the other structures that dup ex_data have
the destination ex_data new'd before the dup.

Reviewed-by: Andy Polyakov <appro@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3568)