[base-cluster/backup] node-agent containerSecurityContext

[cwrau]

Now that #812 has been merged, we should be able to add

--- a/charts/base-cluster/templates/backup/velero.yaml
+++ b/charts/base-cluster/templates/backup/velero.yaml
@@ -41,7 +41,7 @@ spec:
       runAsUser: 1000
       runAsGroup: 1000
       runAsNonRoot: true
-    containerSecurityContext:
+    containerSecurityContext: &containerSecurityContext
       readOnlyRootFilesystem: true
       privileged: false
       capabilities:
@@ -56,6 +56,7 @@ spec:
     nodeAgent:
       resources: {{- .Values.backup.nodeAgent.resources | toYaml | nindent 8 }}
       priorityClassName: system-cluster-critical
+      containerSecurityContext: *containerSecurityContext
     configuration:
       defaultBackupStorageLocation: {{ .Values.backup.defaultLocation | quote }}
       backupStorageLocation: {{- range $name, $spec := .Values.backup.backupStorageLocations }}
diff --git a/charts/base-cluster/values.yaml b/charts/base-cluster/values.yaml
index 1969372..d8f3f00 100644

but this should be tested.