ERR: preserve system error number in a few more places

It turns out that intialization may change the error number, so we
need to preserve the system error number in functions where
initialization is called for.
These are ERR_get_state() and err_shelve_state()

Fixes #7897

Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7902)

(cherry picked from commit 91c5473035aaf2c0d86e4039c2a29a5b70541905)