use set rather than put, recommendation from hazelcast

Signed-off-by: olivier lamy <olamy@webtide.com>

jetty-hazelcast/src/main/java/org/eclipse/jetty/hazelcast/session/HazelcastSessionDataStore.java

@@ -110,7 +110,7 @@ public class HazelcastSessionDataStore
     public void doStore( String id, SessionData data, long lastSaveTime )
         throws Exception
     {
-        this.sessionDataMap.put( getCacheKey( id ), data);
+        this.sessionDataMap.set( getCacheKey( id ), data);
     }
 
     @Override