javax/swing/JToolBar/4529206/bug4529206.java: setFloating does not work correctly

The test `javax/swing/JToolBar/4529206/bug4529206.java` intermittently fails on *Linux* with the following diagnostic:
```
#section:main
----------messages:(5/182)----------
command: main bug4529206
reason: User specified action: run main bug4529206
Mode: othervm
Additional options from @modules: --add-modules java.desktop
elapsed time (seconds): 0.463
----------configuration:(3/40)----------
Boot Layer
  add modules: java.desktop

----------System.out:(0/0)----------
----------System.err:(31/2236)----------
java.lang.reflect.InvocationTargetException
at java.desktop/java.awt.EventQueue.invokeAndWait(EventQueue.java:1379)
at java.desktop/java.awt.EventQueue.invokeAndWait(EventQueue.java:1354)
at java.desktop/javax.swing.SwingUtilities.invokeAndWait(SwingUtilities.java:1480)
at bug4529206.main(bug4529206.java:85)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at com.sun.javatest.regtest.agent.MainWrapper$MainThread.run(MainWrapper.java:127)
at java.base/java.lang.Thread.run(Thread.java:833)
Caused by: java.lang.RuntimeException: setFloating does not work correctly
at bug4529206$3.run(bug4529206.java:88)
at java.desktop/java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:308)
at java.desktop/java.awt.EventQueue.dispatchEventImpl(EventQueue.java:779)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:730)
at java.desktop/java.awt.EventQueue$4.run(EventQueue.java:724)
at java.base/java.security.AccessController.doPrivileged(AccessController.java:399)
at java.base/java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(ProtectionDomain.java:86)
at java.desktop/java.awt.EventQueue.dispatchEvent(EventQueue.java:749)
at java.desktop/java.awt.EventDispatchThread.pumpOneEventForFilters(EventDispatchThread.java:207)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForFilter(EventDispatchThread.java:128)
at java.desktop/java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:117)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:113)
at java.desktop/java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:105)
at java.desktop/java.awt.EventDispatchThread.run(EventDispatchThread.java:92)

JavaTest Message: Test threw exception: java.lang.reflect.InvocationTargetException
JavaTest Message: shutting down test

STATUS:Failed.`main' threw exception: java.lang.reflect.InvocationTargetException
```

The issue was observed with 20-ea+2-50, 17+35-2724

*Reproducibility*: ~30%
*Steps to reproduce*:
```
#!/bin/bash

__test_jdk=$JAVA_HOME
__tests=test/jdk/javax/swing/JToolBar/4529206/bug4529206.java
__count=30

i=0
while true; do
   ((i=i+1))
  echo i: $i
   jtreg/bin/jtreg -v -a -testjdk:$__test_jdk $__tests || break
  if [ "$i" -ge "$__count" ]; then
    break
  fi
done
```