RAND_write_file(): Avoid potential file descriptor leak

If fdopen() call fails we need to close the fd. Also
return early as this is most likely some fatal error.

Fixes #25064

Reviewed-by: Tom Cosgrove <tom.cosgrove@arm.com>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/25081)

(cherry picked from commit d6048344)