Add node IP addresses to DRClusters

Add node IP addresses to DRClusters, enabling fencing prior to application failover.

Procedure

Find the IP addresses for all of the OpenShift nodes in the managed clusters by running this command in the Primary-managed cluster and the Secondary-managed cluster.
```
oc get nodes -o jsonpath='{range .items[*]}{.status.addresses[?(@.type=="ExternalIP")].address}{"\n"}{end}'
```
Example output:
```
10.70.56.118
10.70.56.193
10.70.56.154
10.70.56.242
10.70.56.136
10.70.56.99
```
Once you have the IP addresses then the DRCluster resources can be modified for each managed cluster.

Find the DRCluster names on the Hub Cluster.

oc get drcluster

Example output:

NAME        AGE
ocp4perf1   5m35s
ocp4perf2   5m35s

Edit each DRCluster to add your unique IP addresses, replacing <drcluster_name> with your unique name.

oc edit drcluster <drcluster_name>

apiVersion: ramendr.openshift.io/v1alpha1
kind: DRCluster
metadata:
[...]
spec:
  s3ProfileName: s3profile-<drcluster_name>-ocs-external-storagecluster
  ## Add this section
  cidrs:
    -  <IP_Address1>/32
    -  <IP_Address2>/32
    -  <IP_Address3>/32
    -  <IP_Address4>/32
    -  <IP_Address5>/32
    -  <IP_Address6>/32
[...]

Example output:

drcluster.ramendr.openshift.io/ocp4perf1 edited

Note: There could be more than six IP addresses.

Modify this DRCluster configuration also for IP addresses on the Secondary-managed clusters in the peer DRCluster resource (for example, ocp4perf2).