Fix test_out_option

Random path generation code in test/recipes/15-test_out_option.t
does not work: The code sets rand_path to "/test.pem". I.e. the
test will fail as expected for unprivileged user but will pass
for root user.

Signed-off-by: Patrick Steuer <patrick.steuer@de.ibm.com>

Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/5595)