Mapbox to-image does not work in all environments

[etpinard]

For example:

• http://codepen.io/chriddyp/pen/beBKvo
• https://plot.ly/~jackp/16536/?share_key=xK8wu3y3MavC3tQ7J9puhG
• https://plot.ly/alpha/workspace/

Meanwhile, to-image works fine in the plotly.js test dashboard.

Maybe the problem is related to how we set the ids for each mapbox-gl canvas?

[etpinard]

Looks like the mapboxAccessToken isn't transferred to the cloned graph div on Snapshot.clonePlot which makes to-image fails if the mapbox access token isn't set via Plotly.setPlotConfig. After a quick check, this may not be the end of the story this bug, but it will be a good start.

[etpinard]

This bug appears to be fixed in 1.15.0, in Codepen at least: http://codepen.io/etpinard/pen/oLdaXP