Bug 38360810 - [38298007->15.1.1.0.0] remove use of deprecated ThreadGroup methods in the Coherence Daemon class

(merge 15.1.1-0 -> ce/15.1.1-0 118480)

[git-p4: depot-paths = "//dev/coherence-ce/release/coherence-ce-v15.1.1.0/": change = 118481]

Author: thegridman

prj/coherence-core/src/main/java/com/tangosol/util/Daemon.java

@@ -750,10 +750,7 @@ protected void configureWorker(DaemonWorker worker)
         ThreadGroup curThreadGroup = ensureThreadGroup();
         synchronized (curThreadGroup) // ensures that the thread group is not destroyed concurrently
             {
-            if (curThreadGroup.isDestroyed())
-                {
-                ensureThreadGroup();
-                }
+            ensureThreadGroup();
             threadWorker = makeThread(m_threadGroup, worker, null);
             }
 
@@ -784,11 +781,9 @@ protected void configureWorker(DaemonWorker worker)
     protected ThreadGroup ensureThreadGroup()
         {
         ThreadGroup threadGroup = m_threadGroup;
-        if (threadGroup == null || threadGroup.isDestroyed())
+        if (threadGroup == null)
             {
             threadGroup = m_threadGroup = new ThreadGroup(getConfiguredName());
-            // Make it a daemon so that it is destroyed automatically.
-            threadGroup.setDaemon(true);
             }
         return threadGroup;
         }