Fixup variable name thats install nginx grafana dashboard

[ginta1337]

As for now nginx grafana dashboard is installed in provisioning config directory, not in dashboards one.
To fix this new configuration option was introduced in grafana role.

[spantaleev]

Has something changed in newer Grafana versions to make this necessary? Why do we need to do this?

I have not heard of people complaining about dashboards missing, but it may be that no one has reported it or I've missed it.

[ginta1337]

The command-line argument cfg:default.paths.provisioning= controls where Grafana searches for the provisioning configuration directory structure, and by default, this is /etc/grafana/provisioning inside the container. The dashboard search path is defined in /etc/grafana/provisioning/dashboards/default.yaml as /etc/grafana/dashboards.

The Ansible variable grafana_provisioning_dashboard_providers controls the content of default.yaml, while the variable grafana_provisioning_dashboard_template_files allows additional provisioning configuration files to be placed in the same directory. The dashboard provisioning syntax is described here.

It is incorrect to place exported dashboards in the provisioning configuration path. I hope this clarifies the origin of this obvious issue. Additionally, redefining the grafana_dashboard_files variable can help users add their custom dashboards more effectively.