Clean up the Publisher interface and implementations

A message publisher is enabled when it is connected, which implies an
open Session.

Remove Publisher methods:
* enable - unused
* disable - unused
* getSession - unused
* isEnable - Only used by MessagePublisher internally

MessagePublisher, rename isEnable -> isConnected and make private.

Change-Id: Icc6d73f41f250e5376a2a4b1cb7f82c40ec721ff
diff --git a/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/message/MessagePublisher.java b/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/message/MessagePublisher.java
index 607f4d2..afa716f 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/message/MessagePublisher.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/message/MessagePublisher.java
@@ -45,7 +45,6 @@
   private final Properties properties;
   private final Gson gson;
   private final Timer monitorTimer = new Timer();
-  private boolean available = true;
   private EventListener eventListener;
   private final LinkedBlockingQueue<Event> queue = new LinkedBlockingQueue<>(MAX_EVENTS);
   private CancelableRunnable publisher;
@@ -82,10 +81,10 @@
           public void run() {
             while (!canceled) {
               try {
-                if (isEnable() && session.isOpen()) {
+                if (isConnected()) {
                   Event event = queue.poll(200, TimeUnit.MILLISECONDS);
                   if (event != null) {
-                    if (isEnable() && session.isOpen()) {
+                    if (isConnected()) {
                       publishEvent(event);
                     } else {
                       queue.put(event);
@@ -119,13 +118,13 @@
   public void start() {
     publisherThread = new Thread(publisher);
     publisherThread.start();
-    if (!session.isOpen()) {
+    if (!isConnected()) {
       session.connect();
       monitorTimer.schedule(
           new TimerTask() {
             @Override
             public void run() {
-              if (!session.isOpen()) {
+              if (!isConnected()) {
                 LOGGER.info("#start: try to reconnect");
                 session.connect();
               }
@@ -133,7 +132,6 @@
           },
           MONITOR_FIRSTTIME_DELAY,
           properties.getSection(Monitor.class).interval);
-      available = true;
     }
   }
 
@@ -149,27 +147,6 @@
       }
     }
     session.disconnect();
-    available = false;
-  }
-
-  @Override
-  public void enable() {
-    available = true;
-  }
-
-  @Override
-  public void disable() {
-    available = false;
-  }
-
-  @Override
-  public boolean isEnable() {
-    return available;
-  }
-
-  @Override
-  public Session getSession() {
-    return session;
   }
 
   @Override
@@ -187,6 +164,10 @@
     return this.eventListener;
   }
 
+  private boolean isConnected() {
+    return session != null && session.isOpen();
+  }
+
   private void publishEvent(Event event) {
     session.publish(gson.toJson(event));
   }
diff --git a/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/message/Publisher.java b/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/message/Publisher.java
index b74b94c..f782b00 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/message/Publisher.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/rabbitmq/message/Publisher.java
@@ -2,21 +2,12 @@
 
 import com.google.gerrit.common.EventListener;
 import com.googlesource.gerrit.plugins.rabbitmq.config.Properties;
-import com.googlesource.gerrit.plugins.rabbitmq.session.Session;
 
 public interface Publisher {
   void start();
 
   void stop();
 
-  void enable();
-
-  void disable();
-
-  boolean isEnable();
-
-  Session getSession();
-
   Properties getProperties();
 
   String getName();