IllegalStateException due to Duplicate key in MeterManager.java

IllegalStateException appears in MeterManager.java whenever trying to add/remove a Meter with MeterId equal to an already existing Meter in another device. (Note: In contrast to other Ids, MeterIds are unique just within each device).

The attached log file shows what happens a MeterId with id=1 has already been created in device of:0000000000000001 and one attempts to create another one in of:0000000000000004 (also with id=1).

A similar situation happens when one tries to remove meters that have the same ids in different devices.

The issue appears to be in the pushMeterMetrics method and in particular in the storedMeterMap which uses MeterId as the key.