Provisioning: Show relative path when trying to save provisioned dashboard

[bergquist]

When the user tries to save a provisioned dashboard they get a modal explaining why they cannot save it.

That popup does not explain where to find that dashboards. If the uid and the filename doesnt match it can be quite frustrating to find the dashboard. Grafana currently stores the full path to the dashboard where it runs but we dont want to show that since it might be sensitive information. But we could show the user the relative path of the dashboards to make it easier to find the dashboard.

While we want to create a better workflow for this in the long run. This small change might make it more bearable until we figure it all out.