Tune the log of refuse session request.

The log:
Refusing session request for client as it has seen zxid our last zxid is 0x0 client must try another server (org.apache.zookeeper.server.ZooKeeperServer)

We would better print the sessionId in the content.

After improvement:
Refusing session(0xab) request for client as it has seen zxid our last zxid is 0x0 client must try another server (org.apache.zookeeper.server.ZooKeeperServer)