Fix guarding macro in include/internal/sockets.h
Fix guarding macro in include/internal/sockets.h

The guard was checked but never defined.  Also, rename it to reflect
that this is an internal header file, not a public one.

Reviewed-by: Rich Salz <c04971a99e5a9ee80eaab4b1deb37e845b0bd697@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4254)

openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl,openssl/openssl