Revert "remove superfluent counter and fix log message (apache#6313)"

This reverts commit a9bbcf8.

Author: DaanHoogland

server/src/main/java/com/cloud/api/ApiSessionListener.java

@@ -33,12 +33,17 @@ public class ApiSessionListener implements HttpSessionListener, ServletRequestLi
     public static final Logger LOGGER = Logger.getLogger(ApiSessionListener.class.getName());
     private static final String ATTRIBUTE_NAME = "SessionCounter";
     private static Map<HttpSession, Object> sessions = new ConcurrentHashMap<>();
+    private static long sessionCount;
+
+    public ApiSessionListener() {
+        sessionCount = 0;
+    }
 
     /**
      * @return the internal adminstered session count
      */
     public static long getSessionCount() {
-        return sessions.size();
+        return sessionCount;
     }
 
     /**
@@ -52,15 +57,17 @@ public void sessionCreated(HttpSessionEvent event) {
         synchronized (this) {
             HttpSession session = event.getSession();
             sessions.put(session, event.getSource());
+            sessionCount++;
         }
-        LOGGER.debug("Sessions count: " + getSessionCount());
+        LOGGER.debug("Sessions count: " + sessions);
     }
     public void sessionDestroyed(HttpSessionEvent event) {
         LOGGER.debug("Session destroyed by Id : " + event.getSession().getId() + " , session: " + event.getSession().toString() + " , source: " + event.getSource().toString() + " , event: " + event.toString());
         synchronized (this) {
+            sessionCount--;
             sessions.remove(event.getSession());
         }
-        LOGGER.debug("Sessions count: " + getSessionCount());
+        LOGGER.debug("Sessions count: " + sessions);
     }
 
     @Override