Vertical modebars with wrapped buttons don't honor `modebar.bgcolor`

[antoinerg]

As shown in this Codepen: https://codepen.io/anon/pen/KJawXR

[antoinerg]

The reason we hit this issue is that all modern browsers do not respect the spec and do not grow the width of flex containers that wrap in column mode.

[etpinard]

@antoinerg this one got fixed in #3500 too, right?

[antoinerg]

Yes it did! In #3500 we now style the background color of the button groups instead of the parent container which does not grow its width.