YARN-7678. Ability to enable logging of container memory stats. Contributed by Jim Brennan

(cherry picked from commit 42964c2a66cfe6d7885c6231a2ec7dbde324eb67)

Conflicts:
	hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/monitor/ContainersMonitorImpl.java

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-server/hadoop-yarn-server-nodemanager/src/main/java/org/apache/hadoop/yarn/server/nodemanager/containermanager/monitor/ContainersMonitorImpl.java

@@ -48,8 +48,10 @@ import com.google.common.base.Preconditions;
 public class ContainersMonitorImpl extends AbstractService implements
     ContainersMonitor {
 
-  final static Log LOG = LogFactory
-      .getLog(ContainersMonitorImpl.class);
+  private final static Log LOG =
+      LogFactory.getLog(ContainersMonitorImpl.class);
+  private final static Log AUDITLOG =
+      LogFactory.getLog(ContainersMonitorImpl.class.getName()+".audit");
 
   private long monitoringInterval;
   private MonitoringThread monitoringThread;
@@ -463,8 +465,8 @@ public class ContainersMonitorImpl extends AbstractService implements
             long curRssMemUsageOfAgedProcesses = pTree.getRssMemorySize(1);
             long vmemLimit = ptInfo.getVmemLimit();
             long pmemLimit = ptInfo.getPmemLimit();
-            if (LOG.isDebugEnabled()) {
-              LOG.debug(String.format(
+            if (AUDITLOG.isDebugEnabled()) {
+              AUDITLOG.debug(String.format(
                   "Memory usage of ProcessTree %s for container-id %s: ",
                   pId, containerId.toString()) +
                   formatUsageString(