[MetricsAdvisor] Service returns 0 CustomFillValue even if fill type is not CustomValue

[kinelski]

In DataFeedMissingDataPointFillSettings, CustomFillValue is set only when FillMissingPointType is CustomValue. When the fill type is NOT CustomValue, I'd expect the service to not return the CustomFillValue (or return null). However, it returns 0.0.

Note: remove the workaround we did in the internal DataFeedMissingDataPointFillSettings constructor when this is fixed:

CustomFillValue = dataFeedDetail.FillMissingPointType == DataFeedMissingDataPointFillType.CustomValue
    ? dataFeedDetail.FillMissingPointValue
    : null;

Update it to:

CustomFillValue = dataFeedDetail.FillMissingPointValue;

[kinelski]

Service issue. Closing this since it's not related to the SDK.