Clean up RAND_bytes() calls

When RAND_pseudo_bytes() was replaced with RAND_bytes(), this case
was not reduced to a simple RAND_bytes() call.

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Rich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1117)