Bug 1778451: Show legend in charts

Use correct variable in template when creating the legend for charts.

In Chart.js legendTemplate uses var 'datasets'
or 'segments' depending on the type of charts
  type Doughnut/PolarArea/Pie use segments
  type Line/Radar/Bar use datasets

We have to check which one is defined in the Chart object before
modifying the legend template

Also delayed the updating of page by .5 secs so not to clash with
chart jsons stuff

behatnotneeded

Change-Id: Id3ef35a5037ac2c30d342279e0af7052584f7d16
(cherry picked from commit d09994c2)