Fixed the return code for RAND_egd_bytes.

According to the documentation, the return code should be -1 when
RAND_status does not return 1.

Reviewed-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Richard Levitte <levitte@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/1886)