Ignore the available volume when calling DetachDisk

If use detachs the volume by nova in openstack env, volume becomes
available. If nova instance is been deleted, nova will detach it
automatically. So the "available" is fine since that means the
volume is detached from instance already.

Author: FengyunPan

pkg/cloudprovider/providers/openstack/openstack_volumes.go

@@ -215,11 +215,7 @@ func (os *OpenStack) AttachDisk(instanceID, volumeID string) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	if volume.Status != VolumeAvailableStatus {
-		errmsg := fmt.Sprintf("volume %s status is %s, not %s, can not be attached to instance %s.", volume.Name, volume.Status, VolumeAvailableStatus, instanceID)
-		glog.Errorf(errmsg)
-		return "", errors.New(errmsg)
-	}
+
 	cClient, err := os.NewComputeV2()
 	if err != nil {
 		return "", err
@@ -258,6 +254,12 @@ func (os *OpenStack) DetachDisk(instanceID, volumeID string) error {
 	if err != nil {
 		return err
 	}
+	if volume.Status == VolumeAvailableStatus {
+		// "available" is fine since that means the volume is detached from instance already.
+		glog.V(2).Infof("volume: %s has been detached from compute: %s ", volume.ID, instanceID)
+		return nil
+	}
+
 	if volume.Status != VolumeInUseStatus {
 		errmsg := fmt.Sprintf("can not detach volume %s, its status is %s.", volume.Name, volume.Status)
 		glog.Errorf(errmsg)