ONOS-239 Retrigger compilation when new resources are available

When an intent is withdrawn and frees up resources, trigger
recompilation of any failed intents to allow the ones waiting
for resources to be installed.

Change-Id: Ic15678378ce41516a7eab890b4b4898aeb901f78
diff --git a/core/api/src/main/java/org/onlab/onos/net/resource/LinkResourceStore.java b/core/api/src/main/java/org/onlab/onos/net/resource/LinkResourceStore.java
index 59d1e19..85ee89c 100644
--- a/core/api/src/main/java/org/onlab/onos/net/resource/LinkResourceStore.java
+++ b/core/api/src/main/java/org/onlab/onos/net/resource/LinkResourceStore.java
@@ -44,7 +44,7 @@
      *
      * @param allocations resources to be released
      */
-    void releaseResources(LinkResourceAllocations allocations);
+    LinkResourceEvent releaseResources(LinkResourceAllocations allocations);
 
     /**
      * Returns resources allocated for an Intent.