YARN-4171. Fix findbugs warnings in YARN-1197 branch. Contributed by Wangda Tan

(cherry picked from commit b3f6b641dccb0d59df78855e2951d2cae7dff8ad)

Conflicts:
	hadoop-yarn-project/CHANGES.txt

hadoop-yarn-project/CHANGES.txt

@@ -848,6 +848,8 @@ Release 2.8.0 - UNRELEASED
     YARN-4044. Running applications information changes such as movequeue is not published to 
     TimeLine server. (Sunil G via rohithsharmaks)
 
+    YARN-4171. Fix findbugs warnings in YARN-1197 branch. (Wangda Tan via jianhe)
+
 Release 2.7.2 - UNRELEASED
 
   INCOMPATIBLE CHANGES

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-resourcemanager/src/main/java/org/apache/hadoop/yarn/server/resourcemanager/rmnode/RMNodeStatusEvent.java

@@ -93,6 +93,7 @@ public class RMNodeStatusEvent extends RMNodeEvent {
     this.logAggregationReportsForApps = logAggregationReportsForApps;
   }
   
+  @SuppressWarnings("unchecked")
   public List<Container> getNMReportedIncreasedContainers() {
     return nmReportedIncreasedContainers == null ? Collections.EMPTY_LIST
         : nmReportedIncreasedContainers;

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

@@ -478,9 +478,6 @@ public class SchedulerApplicationAttempt implements SchedulableEntity {
     ContainerType containerType = ContainerType.TASK;
     // The working knowledge is that masterContainer for AM is null as it
     // itself is the master container.
-    RMAppAttempt appAttempt = rmContext.getRMApps()
-        .get(container.getId().getApplicationAttemptId().getApplicationId())
-        .getCurrentAppAttempt();
     if (isWaitingForAMContainer(getApplicationId())) {
       containerType = ContainerType.APPLICATION_MASTER;
     }