HDFS-14923. Remove dead code from HealthMonitor. Contributed by Fei Hui.

Signed-off-by: Wei-Chiu Chuang <weichiu@apache.org>

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/ha/HealthMonitor.java

@@ -137,19 +137,11 @@ public class HealthMonitor {
   public void addCallback(Callback cb) {
     this.callbacks.add(cb);
   }
-  
-  public void removeCallback(Callback cb) {
-    callbacks.remove(cb);
-  }
 
   public synchronized void addServiceStateCallback(ServiceStateCallback cb) {
     this.serviceStateCallbacks.add(cb);
   }
 
-  public synchronized void removeServiceStateCallback(ServiceStateCallback cb) {
-    serviceStateCallbacks.remove(cb);
-  }
-
   public void shutdown() {
     LOG.info("Stopping HealthMonitor thread");
     shouldRun = false;
@@ -261,11 +253,7 @@ public class HealthMonitor {
   synchronized State getHealthState() {
     return state;
   }
-  
-  synchronized HAServiceStatus getLastServiceStatus() {
-    return lastServiceState;
-  }
-  
+
   boolean isAlive() {
     return daemon.isAlive();
   }