Fix keep refreshing partitions issue

In PartitionedTridentSpoutExecutor.Emitter.emitBatch(final TransactionAttempt tx, final Object coordinatorMeta,
                final TridentCollector collector) method, trident will check whether if the coordinatorMeta is the same from the last one.
The GlobalPartitionInformation is the coordinatorMeta passed, and there's no equal() method overried, thus everytime it will refresh the partition even if the broker information is the same in GlobalPartitionInformation.