8281183: RandomGenerator:NextDouble() default behavior partially fixed by JDK-8280950

Reviewed-by: jlaskey

src/java.base/share/classes/jdk/internal/util/random/RandomSupport.java

@@ -677,7 +677,7 @@ public class RandomSupport {
         double r = rng.nextDouble();
         r = r * bound;
         if (r >= bound)  // may need to correct a rounding problem
-            r = Math.nextDown(r);
+            r = Math.nextDown(bound);
         return r;
     }