YARN-9337. Addendum to fix compilation error due to mockito spy call

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/test/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/resourceplugin/gpu/TestGpuDiscoverer.java

@@ -505,7 +505,7 @@ public class TestGpuDiscoverer {
     Configuration conf = new Configuration();
     conf.set(YarnConfiguration.NM_GPU_ALLOWED_DEVICES, "0:1,2:3");
 
-    GpuDiscoverer gpuSpy = spy(GpuDiscoverer.class);
+    GpuDiscoverer gpuSpy = spy(new GpuDiscoverer());
 
     gpuSpy.initialize(conf);
     gpuSpy.getGpusUsableByYarn();