PMM-13023 Add leading slash to home dashboard path (#2939)

Author: matejkubinec

build/ansible/roles/grafana/files/grafana.ini

@@ -53,7 +53,7 @@ default_home_dashboard_path = /usr/share/percona-dashboards/panels/pmm-app/dist/
 #################################### Users ###############################
 [users]
 # Path to a custom home page. Users are only redirected to this if the default home dashboard is used. It should match a frontend route and contain a leading slash.
-home_page = d/pmm-home/home-dashboard
+home_page = /d/pmm-home/home-dashboard
 
 #################################### Anonymous Auth ######################
 [auth.anonymous]