Timechart with time overlay displays an extraneous series with 2 points

[dmehra]

read stochastic -source 'cdn' -source_type 'metric' -last :2 days: -daily .5 name = 'cpu' 
| view timechart 
    -display.duration :1 day:
    -display.overlayTime true

This code produces not 2 but 3 time series, the extra one having 2 points at the left edge of the chart. It goes away if you do -from :2 days ago:+:1 hour: -to :now: instead of -last :2 days:. The problem is likely with the time overlay in the timechart rather than with the stochastic source that gives us the data.

The code is docs/examples/charts/timechart_time_overlay_1.juttle and docs/examples/charts/timechart_time_overlay_2.juttle that are used in the docs article http://juttle.github.io/juttle-viz/charts/timechart/

I used that +:1h: workaround to generate screenshots so the docs page looks ok. However if users run the examples, they'll get the weird extra series.

[dmehra]