Create the .rnd file it it does not exist

It's a bit annoying, since some commands try to read a .rnd file,
and print an error message if the file does not exist.

But previously a .rnd file was created on exit, and that does no longer
happen.

Fixed by continuing in app_RAND_load_conf regardless of the error in
RAND_load_file.

If the random number generator is still not initalized on exit, the
function RAND_write_file will fail and no .rnd file would be created.

Remove RANDFILE from openssl.cnf

Reviewed-by: Kurt Roeckx <kurt@roeckx.be>
(Merged from https://github.com/openssl/openssl/pull/7217)