apps/speed.c: add missing checks for RAND_bytes()

Function RAND_bytes() may return 0 or -1 on error, simply
goto end label when it fails.

Fixes #6567
Reviewed-by: NRich Salz <rsalz@openssl.org>
Reviewed-by: NMatthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/6582)

apps/speed.c

@@ -2557,7 +2557,8 @@ int speed_main(int argc, char **argv)
     }
 
     for (i = 0; i < loopargs_len; i++)
-        RAND_bytes(loopargs[i].buf, 36);
+        if (RAND_bytes(loopargs[i].buf, 36) <= 0)
+            goto end;
 
 #ifndef OPENSSL_NO_RSA
     for (testnum = 0; testnum < RSA_NUM; testnum++) {
@@ -2653,7 +2654,8 @@ int speed_main(int argc, char **argv)
 #endif                          /* OPENSSL_NO_RSA */
 
     for (i = 0; i < loopargs_len; i++)
-        RAND_bytes(loopargs[i].buf, 36);
+        if (RAND_bytes(loopargs[i].buf, 36) <= 0)
+            goto end;
 
 #ifndef OPENSSL_NO_DSA
     for (testnum = 0; testnum < DSA_NUM; testnum++) {