Update mongodb_scalling

CpuAlarmHigh:
    type: AWS::AutoScaling::Trigger
    properties: 
      AutoScalingGroupName: {Ref: MongoDBServerGroup}
      BreachDuration: 60
      Dimensions: 
      statistic: avg
      LowerThreshold: 40
      UpperThreshold: 50
      MetricName: cpu_util
      Namespace:
      Period:
      Statistic:

Need to add several fields