YARN-5444. Fix failing unit tests in TestLinuxContainerExecutorWithMocks. Contributed by Yufei Gu.

(cherry picked from commit 95694b70cd38dfc591dc4f0e9413809cf3c91dbe)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/LinuxContainerExecutor.java

@@ -100,6 +100,7 @@ public class LinuxContainerExecutor extends ContainerExecutor {
             DefaultLCEResourcesHandler.class, LCEResourcesHandler.class), conf);
     resourcesHandler.setConf(conf);
 
+    containerSchedPriorityIsSet = false;
     if (conf.get(YarnConfiguration.NM_CONTAINER_EXECUTOR_SCHED_PRIORITY)
         != null) {
       containerSchedPriorityIsSet = true;

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/test/java/org/apache/hadoop/yarn/server/nodemanager/TestLinuxContainerExecutorWithMocks.java

@@ -142,7 +142,7 @@ public class TestLinuxContainerExecutorWithMocks {
     tmpMockExecutor = System.getProperty("test.build.data") +
         "/tmp-mock-container-executor";
 
-    Configuration conf = new Configuration();
+    Configuration conf = new YarnConfiguration();
     LinuxContainerRuntime linuxContainerRuntime;
     LinuxContainerRuntime mockLinuxContainerRuntime;
 
@@ -236,7 +236,10 @@ public class TestLinuxContainerExecutorWithMocks {
   public void testLaunchCommandWithoutPriority() throws IOException {
     // make sure the command doesn't contain the nice -n since priority
     // not specified
-   List<String> command = new ArrayList<String>();
+    List<String> command = new ArrayList<String>();
+    Configuration conf = mockExec.getConf();
+    conf.unset(YarnConfiguration.NM_CONTAINER_EXECUTOR_SCHED_PRIORITY);
+    mockExec.setConf(conf);
     mockExec.addSchedPriorityCommand(command);
     assertEquals("addSchedPriority should be empty", 0, command.size());
   }
@@ -259,7 +262,7 @@ public class TestLinuxContainerExecutorWithMocks {
           .build());
 
       List<String> result=readMockParams();
-      Assert.assertEquals(result.size(), 18);
+      Assert.assertEquals(result.size(), 19);
       Assert.assertEquals(result.get(0), YarnConfiguration.DEFAULT_NM_NONSECURE_MODE_LOCAL_USER);
       Assert.assertEquals(result.get(1), "test");
       Assert.assertEquals(result.get(2), "0" );