Modify ossl_method_store_add() to handle reference counting

Modify ossl_method_store_add() to handle reference counting

Because this function affects the reference count on failure (the call
to impl_free() does this), it may as well handle incrementing it as
well to indicate the extra reference in the method store.

Reviewed-by: Shane Lontis <shane.lontis@oracle.com>
(Merged from https://github.com/openssl/openssl/pull/9650)