No RBD mirror daemon-related alert when the daemon is down. 


Steps to Reproduce:
1. Enable mirroring at cluster level using the below CLI command:
         oc patch StorageCluster $(oc get StorageCluster -n openshift-storage -o=jsonpath='{.items[0].metadata.name}')  -n openshift-storage --type json --patch  '[{ "op": "replace", "path": "/spec/mirroring", "value": {"enabled": true} }]'

2. Use below script to down rbd mirroring container:

start=$(date +%s.%N)

for i in {1..10}
    do
         x=`oc get pods -n openshift-storage | grep rook-ceph-rbd-mirror-a | awk '{print $1}'`
         oc -n openshift-storage exec $x -c rbd-mirror -- kill 1
         result=`oc get pod $x -n openshift-storage -o=jsonpath='{.status.containerStatuses[1].state.running}'`
         until [ -n "$result" ]
	 do
             echo "Container is down"
             sleep 2s
             result=`oc get pod $x -n openshift-storage -o=jsonpath='{.status.containerStatuses[1].state.running}'`
         done
         echo "Container is running"
         sleep 2s
     done

end=$(date +%s.%N)    
runtime=$(python -c "print(${end} - ${start})")

echo "Runtime was $runtime"

3. (or) another way is to decrease the instance count to 0 in rbd mirror daemon deployment CR (not recommended) 



Actual results:
No RBD mirroring daemon alert was raised even after the mirroring daemon is down. (alert was introduced in 4.9) 
Expected results:

Raise RBd mirroring mirroring daemon alert when daemon is down
Additional info: