YARN-6381. FSAppAttempt has several variables that should be final

(Contributed by Ameet Zaveri via Daniel Templeton)

(cherry picked from commit 984df31a31c25ffc8541467dc41913f62f69e1df)

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/scheduler/fair/FSAppAttempt.java

@@ -73,11 +73,11 @@ public class FSAppAttempt extends SchedulerApplicationAttempt
   private static final DefaultResourceCalculator RESOURCE_CALCULATOR
       = new DefaultResourceCalculator();
 
-  private long startTime;
-  private Priority appPriority;
-  private ResourceWeights resourceWeights;
+  private final long startTime;
+  private final Priority appPriority;
+  private final ResourceWeights resourceWeights;
   private Resource demand = Resources.createResource(0);
-  private FairScheduler scheduler;
+  private final FairScheduler scheduler;
   private FSQueue fsQueue;
   private Resource fairShare = Resources.createResource(0, 0);
 
@@ -95,9 +95,9 @@ public class FSAppAttempt extends SchedulerApplicationAttempt
 
   // Used to record node reservation by an app.
   // Key = RackName, Value = Set of Nodes reserved by app on rack
-  private Map<String, Set<String>> reservations = new HashMap<>();
+  private final Map<String, Set<String>> reservations = new HashMap<>();
 
-  private List<FSSchedulerNode> blacklistNodeIds = new ArrayList<>();
+  private final List<FSSchedulerNode> blacklistNodeIds = new ArrayList<>();
   /**
    * Delay scheduling: We often want to prioritize scheduling of node-local
    * containers over rack-local or off-switch containers. To achieve this