Non-IB image in Grafana chart

This chart has a dependency on the Grafana 6.4.* chart as seen here.

This chart is bundled with version 6.4.8.

The Grafana 6.4.8 chart has a value to specify the downloadDashboardsImage as seen here which defaults to curlimages/curl:7.73.0.

We should find/build a suitable hardened IB image and override these default values. It looks as though anything will curl will work fine. The script being executed by this job can be found here.