Fake BIO_snprintf() does not actually print anything to buf,
it should return -1 as error.
0 will be considered a correct return value, the consumer may think that
the buf is valid and parse the buffer.
please refer to bugzilla link for details.
Cc: Jiewen Yao <jiewen.yao@intel.com> Cc: Jian J Wang <jian.j.wang@intel.com> Cc: Xiaoyu Lu <xiaoyu1.lu@intel.com> Cc: Guomin Jiang <guomin.jiang@intel.com> Signed-off-by: Yi Li <yi1.li@intel.com> Reviewed-by: Jiewen Yao <Jiewen.yao@intel.com>