Removing isEventDispatchThread - it causes problems in headless env

[JaroslavTulach]

A colleague of mine reported following error when using Sampler:

Caused by: java.awt.AWTError: Could not create Toolkit: sun.awt.X11.XToolkit
    at java.desktop/java.awt.Toolkit$2.run(Toolkit.java:607)
    at java.desktop/java.awt.Toolkit$2.run(Toolkit.java:583)
    at java.base/java.security.AccessController.doPrivileged(Native Method)
    at java.desktop/java.awt.Toolkit.getDefaultToolkit(Toolkit.java:582)
    at java.desktop/java.awt.Toolkit.getEventQueue(Toolkit.java:1494)
    at java.desktop/java.awt.EventQueue.isDispatchThread(EventQueue.java:1086)
    at java.desktop/javax.swing.SwingUtilities.isEventDispatchThread(SwingUtilities.java:1493)
    at org.netbeans.modules.sampler.Sampler.stopSampling(Sampler.java:232)
    at org.netbeans.modules.sampler.Sampler.stopAndWriteTo(Sampler.java:209)
    at org.netbeans.modules.sampler.Test.stopSampling(Test.java:58)
    at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    ... 1 more

We shouldn't be calling into Swing in a library that is supposed to be used in a headless environment. Removing the (almost useless) check.

With this PR I can build the org-netbeans-modules-sampler.jar and run Test.java as:

/jdk-11/bin/java -cp ~/NetBeansProjects/netbeans/nbbuild/netbeans/platform/modules/org-netbeans-modules-sampler.jar Test.java
Starting processing ...
Processing started
doing work ...
doing work ...
doing work ...
doing work ...
doing work ...
^CRunning shutdown hook.
Stopping sampling ...
Sampling stopped.

while doing the same with d5f29c1 yields the above described error.

[ebarboni]

Hi sorry for the delay, but as said in the ML the delivery branches is not accurate. It contains spec version of NetBeans 15. (as well of other master changes). We had a conflig merging delivery to master and I did'nt see the impact.

@neilcsmith-net @JaroslavTulach maybe this PR can be rebase to release140, and we could create a sync PR to get this to master.
I could generate a RC5 and on wednesday I should be able to generate the bits for voting.

[neilcsmith-net]

@ebarboni syncing release140 with master would be a problem. Best to fix delivery as @matthiasblaesing outlined. Alternatively merge this direct to release140 and @JaroslavTulach can open a second PR for just this change against master. Shouldn't cause a problem ... if the vote goes to plan.

[ebarboni]

sorry @neilcsmith-net I guess the delivery is good now.

[ebarboni]

@JaroslavTulach I guess you have to rebase this PR on the up to date delivery branch.