Fix ListenerWithFilter test

src/System.Diagnostics.TextWriterTraceListener/tests/XmlWriterTraceListenerTests.cs

@@ -103,15 +103,16 @@ public void Close_AfterXPathNavigatorTraced()
         [Fact]
         public void ListenerWithFilter()
         {
-            int processId;
+            // Ensure we use an arbitrary ID that doesn't match the process ID or thread ID.
+            int traceTransferId = 1;
             using (Process p = Process.GetCurrentProcess())
             {
-                processId = p.Id;
+                while (traceTransferId == p.Id || traceTransferId == Environment.CurrentManagedThreadId)
+                {
+                    traceTransferId++;
+                }
             }
 
-            // Ensure we use an arbitrary ID that doesn't match the process ID.
-            int traceTransferId = processId + 1;
-
             string file = GetTestFilePath();
             Guid guid = Guid.NewGuid();
             using (var listener = new XmlWriterTraceListener(file))