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
diff --git a/core/api/src/main/java/org/onosproject/net/meter/MeterId.java b/core/api/src/main/java/org/onosproject/net/meter/MeterId.java
index 872de2d..43c4141 100644
--- a/core/api/src/main/java/org/onosproject/net/meter/MeterId.java
+++ b/core/api/src/main/java/org/onosproject/net/meter/MeterId.java
@@ -19,7 +19,7 @@
 
 /**
  * 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 {