Don't use a ssl specific DRBG anymore

Since the public and private DRBG are per thread we don't need one
per ssl object anymore. It could also try to get entropy from a DRBG
that's really from an other thread because the SSL object moved to an
other thread.

Reviewed-by: Tim Hudson <tjh@openssl.org>
Reviewed-by: Paul Dale <paul.dale@oracle.com>
Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/5547)

ssl/s3_lib.c

diff --git a/ssl/s3_lib.c b/ssl/s3_lib.c
index f230b5f..bbf49a2 100644
--- a/ssl/s3_lib.c
+++ b/ssl/s3_lib.c
@@ -4524,12 +4524,12 @@
         unsigned char *p = result;
 
         l2n(Time, p);
-        ret = ssl_randbytes(s, p, len - 4);
+        ret = RAND_bytes(p, len - 4);
     } else {
-        ret = ssl_randbytes(s, result, len);
+        ret = RAND_bytes(result, len);
     }
 #ifndef OPENSSL_NO_TLS13DOWNGRADE
-    if (ret) {
+    if (ret > 0) {
         if (!ossl_assert(sizeof(tls11downgrade) < len)
                 || !ossl_assert(sizeof(tls12downgrade) < len))
              return 0;