6997495: correction of regression test compiler/6857159/Test6857159

Summary: Testcase correction.
Reviewed-by: never

test/compiler/6857159/Test6857159.java

@@ -54,7 +54,7 @@ public class Test6857159 extends Thread {
     }
 
     public static void main(String[] args) throws Exception {
-        for (int i = 0; i < 100000; i++) {
+        for (int i = 0; i < 20000; i++) {
             Thread t = null;
             switch (i % 3) {
               case 0: t = new ct0(); break;