Description of problem:
Per engineering, a node (hostname/IP) has to be added to the inventory under the [grafana-server] group when deloying with ceph-ansible, otherwise, the run will end up with the following error: "you must add a [grafana-server] group and add at least one node." or if the group is defined but empty: "you must add at least one node in the [grafana-server] hosts group"



Version-Release number of selected component (if applicable):
4.0 beta 2 drop (v4.0.0rc13)

How reproducible:


Steps to Reproduce:
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Actual results:
Customer receives error: "you must add a [grafana-server] group and add at least one node." or if the group is defined but empty: "you must add at least one node in the [grafana-server] hosts group"

Expected results:
Dashboard is deployed without error.

Additional info:
Customers should avoid colocating ceph-mgr and grafana when deploying with ceph-ansible. To prevent this situation, the following text should be added as a prereq to section 5.2: 

"Before installing with ceph-ansible, edit the inventory file and specify a node (hostname or IP address) under the [grafana-server] group where the Grafana and Prometheus instance for the Dashboard will be installed."