Style change of def starting with if

* When a def starts with if and is not a oneliner the if
  should be on a new line.
* The reason is that it might be easy to miss the if when
  reading the code.

akka-cluster/src/main/scala/akka/cluster/ClusterReadView.scala

@@ -143,8 +143,8 @@ private[akka] class ClusterReadView(cluster: Cluster) extends Closeable {
   /**
    * Unsubscribe to cluster events.
    */
-  def close(): Unit = if (!eventBusListener.isTerminated) {
-    eventBusListener ! PoisonPill
-  }
+  def close(): Unit =
+    if (!eventBusListener.isTerminated)
+      eventBusListener ! PoisonPill
 
 }