Remove double fetch of "OSSL_EX_DATA_GLOBAL" for global lock

Remove double fetch of "OSSL_EX_DATA_GLOBAL" for global lock

Fetch once and just pass the global ex_data to the "get_and_lock" static
function.

Removed a redundant null pointer check within the "get_and_lock" static
function (control already performed by the caller).

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
Reviewed-by: Tomas Mraz <tmraz@fedoraproject.org>
(Merged from https://github.com/openssl/openssl/pull/11152)