[21u] strace006 can fail due to unexpected stack length

# ERROR: Unexpected 1 element of the stack trace:
# ERROR: jdk.internal.event.ThreadSleepEvent.<init>
Snapshot of thread: 0
0: jdk.internal.event.Event.<init>(Event.java:39)
1: jdk.internal.event.ThreadSleepEvent.<init>(ThreadSleepEvent.java:32)
2: jdk.internal.event.ThreadSleepEvent.<clinit>(ThreadSleepEvent.java:33)
3: java.lang.Thread.beforeSleep(Thread.java:456)
4: java.lang.Thread.sleep(Thread.java:504)
5: nsk.monitoring.stress.thread.RunningThread.waitForSign(strace001.java:410)
6: nsk.monitoring.stress.thread.RunningThread.recursionNative(Native Method)
7: nsk.monitoring.stress.thread.RunningThread.recursionNative(Native Method)