Remove warning.

Author: Steve Powell

src/com/rabbitmq/tools/Tracer.java

@@ -31,7 +31,6 @@
 import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicBoolean;
-import java.util.concurrent.atomic.AtomicInteger;
 
 import com.rabbitmq.client.AMQP;
 import com.rabbitmq.client.impl.AMQCommand;