Reset Grafana admin password if it changes

Summary

Grafana does not update the admin password from the configuration file if it is added or updated. We can trigger an update of the password via grafana-cli admin reset-admin-password.

Proposal

When a user updates grafana['admin_password'] in gitlab.rb, we could trigger a password reset cycle of the Grafana admin account.

References

http://docs.grafana.org/administration/cli/#reset-admin-password