[ONOS-3601] Add unit test for MetricCodec and correct some typos

Change-Id: I72317b3d2ea8c428bcc24aa215ae97c098a38305
diff --git a/core/common/src/test/java/org/onosproject/codec/impl/MeterCodecTest.java b/core/common/src/test/java/org/onosproject/codec/impl/MeterCodecTest.java
index dcabcc4..476785d 100644
--- a/core/common/src/test/java/org/onosproject/codec/impl/MeterCodecTest.java
+++ b/core/common/src/test/java/org/onosproject/codec/impl/MeterCodecTest.java
@@ -51,7 +51,7 @@
     final CoreService mockCoreService = createMock(CoreService.class);
 
     /**
-     * Sets up for each test.  Creates a context and fetches the flow rule
+     * Sets up for each test.  Creates a context and fetches the meter
      * codec.
      */
     @Before