Add missing file for.

Add event to signal when all switches have reconnected after failover

src/main/java/net/floodlightcontroller/core/IReadyForReconcileListener.java

+package net.floodlightcontroller.core;
+
+/**
+ * This listener is a temporary solution to start flow reconciliation
+ * after a Slave -> Master transition. It is fired once all known switches are
+ * active (either because they all reconnected or because they did not
+ * reconnect and have timed out).
+ *
+ * Modules should generally not rely on this notification unless there are
+ * strong and compelling reasons to do so. I general modules should handle
+ * the fact that some known switches are not active!
+ * @author gregor
+ *
+ */
+public interface IReadyForReconcileListener {
+    public void readyForReconcile();
+}