fix some of findbugs issues

Change-Id: I20aa54af16f3a1e3323d735fe53cc26c03d5e52e
diff --git a/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleHostStore.java b/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleHostStore.java
index ef80b72..ee8570d 100644
--- a/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleHostStore.java
+++ b/core/store/trivial/src/main/java/org/onlab/onos/store/trivial/impl/SimpleHostStore.java
@@ -269,7 +269,7 @@
     }
 
     // Auxiliary extension to allow location to mutate.
-    private class StoredHost extends DefaultHost {
+    private static final class StoredHost extends DefaultHost {
         private HostLocation location;
 
         /**