Add InstanceExists* methods to cloud provider interface for CCM

pkg/cloudprovider/providers/azure/azure_instances.go

@@ -17,6 +17,7 @@ limitations under the License.
 package azure
 
 import (
+	"errors"
 	"fmt"
 
 	"k8s.io/api/core/v1"
@@ -86,6 +87,11 @@ func (az *Cloud) ExternalID(name types.NodeName) (string, error) {
 	return az.InstanceID(name)
 }
 
+// InstanceExistsByProviderID returns true if the instance with the given provider id still exists and is running.
+func (az *Cloud) InstanceExistsByProviderID(providerID string) (bool, error) {
+	return false, errors.New("unimplemented")
+}
+
 func (az *Cloud) isCurrentInstance(name types.NodeName) (bool, error) {
 	nodeName := mapNodeNameToVMName(name)
 	metadataName, err := az.metadata.Text("instance/compute/name")