Enforce ReadWriteOncePod access mode during scheduling

Check the PVC ref count on the node info cache to determine if a pod's
PVCs are in use. If they are and it is using ReadWriteOncePod, fail the
request.

pkg/scheduler/framework/plugins/feature/feature.go

@@ -23,4 +23,5 @@ type Features struct {
 	EnablePodAffinityNamespaceSelector bool
 	EnablePodDisruptionBudget          bool
 	EnablePodOverhead                  bool
+	EnableReadWriteOncePod             bool
 }