Add logging to CleanupTask

The code for the CleanupTask in the HA-plugin contained logging. These
logging statements are now also implemented here.

Change-Id: Iba03e51fcfba421b93b6e07d1298e2cb121c18f9
diff --git a/src/main/java/com/googlesource/gerrit/plugins/websession/flatfile/FlatFileWebSessionCacheCleaner.java b/src/main/java/com/googlesource/gerrit/plugins/websession/flatfile/FlatFileWebSessionCacheCleaner.java
index 5c88f92..64d1e70 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/websession/flatfile/FlatFileWebSessionCacheCleaner.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/websession/flatfile/FlatFileWebSessionCacheCleaner.java
@@ -17,6 +17,7 @@
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static java.util.concurrent.TimeUnit.SECONDS;
 
+import com.google.common.flogger.FluentLogger;
 import com.google.gerrit.extensions.annotations.PluginName;
 import com.google.gerrit.extensions.events.LifecycleListener;
 import com.google.gerrit.server.git.WorkQueue;
@@ -34,6 +35,7 @@
   private ScheduledFuture<?> scheduledCleanupTask;
 
   static class CleanupTask implements Runnable {
+    private static final FluentLogger log = FluentLogger.forEnclosingClass();
     private final FlatFileWebSessionCache flatFileWebSessionCache;
     private final String pluginName;
 
@@ -45,7 +47,9 @@
 
     @Override
     public void run() {
+      log.atInfo().log("Cleaning up expired file based websessions...");
       flatFileWebSessionCache.cleanUp();
+      log.atInfo().log("Cleaning up expired file based websessions...Done");
     }
 
     @Override