Fixed issue in MeterManager.java

- Added check in pushMeterMetrics method to delete Meter only when it is in the PENDING_REMOVE state
- Minor change: Corrected description in MeterId.java to indicate that MeterIds are unique only within a device

Change-Id: I40e8a0cfaa93884b026e899e9c879e22133ba63b

@@ -19,7 +19,7 @@ import static com.google.common.base.Preconditions.checkArgument;
 
 /**
  * A representation of a meter id.
- * Uniquely identifies a meter system wide.
+ * Uniquely identifies a meter in the scope of a single device.
  */
 public final class MeterId {
 

@@ -222,7 +222,7 @@ public class MeterManager extends AbstractListenerProviderRegistry<MeterEvent, M
                     provider().performMeterOperation(m.deviceId(),
                                                      new MeterOperation(m,
                                                                         MeterOperation.Type.ADD));
-                } else {
+                } else if ((m.state() == MeterState.PENDING_REMOVE)) {
                     store.deleteMeterNow(m);
                 }
             });