dashboard: run dashboard role on mgr/mon nodes

We don't need to execute the ceph-dashboard role on the nodes present
in the grafana-server group. This one is dedicated to the grafana and
prometheus stack.
The ceph-dashboard needs to executed where the ceph-mgr is running. It
is either on the dedicated mgr nodes or if mgr and mon are collocated
implicitly on the mon nodes.

Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>

infrastructure-playbooks/dashboard.yml

@@ -67,7 +67,7 @@
             status: "Complete"
             end: "{{ lookup('pipe', 'date +%Y%m%d%H%M%SZ') }}"
 
-- hosts: "{{ grafana_server_group_name }}"
+- hosts: "{{ groups[mgr_group_name] | default(groups[mon_group_name]) }}"
   become: true
   pre_tasks:
     - name: set ceph dashboard install 'In Progress'