Fix a RUN_ONCE bug

We have a number of instances where there are multiple "init" functions for
a single CRYPTO_ONCE variable, e.g. to load config automatically or to not
load config automatically. Unfortunately the RUN_ONCE mechanism was not
correctly giving the right return value where an alternative init function
was being used.

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7983)