Fix issues found by FindBugs: SIC_INNER_SHOULD_BE_STATIC

http://findbugs.sourceforge.net/bugDescriptions.html#SIC_INNER_SHOULD_BE_STATIC

Change-Id: I9026bed7bb5f3f5cbab08d3277802f25b8d2659e
diff --git a/src/main/java/net/onrc/onos/core/intent/IntentMap.java b/src/main/java/net/onrc/onos/core/intent/IntentMap.java
index 0bba44b..9bdb21f 100644
--- a/src/main/java/net/onrc/onos/core/intent/IntentMap.java
+++ b/src/main/java/net/onrc/onos/core/intent/IntentMap.java
@@ -39,7 +39,7 @@
         STATE_CHANGED,
     }
 
-    public class ChangedEvent {
+    public static class ChangedEvent {
         public ChangedEvent(ChangedEventType eventType, Intent intent) {
             this.eventType = eventType;
             this.intent = intent;