Fix a mem leak in the ocsp app

Free memory allocated in the parent process that is not needed in the
child. We also free it in the parent. Technically this isn't really
required since we end up calling exit() soon afterwards - but to
prevent false positives we free it anyway.

Fixes a Coverity issue.

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7335)