Make migrate-one-vm-to-regular command idempotent

uncloud/uncloud_vm/migrations/0014_vmproduct_vmid.py

@@ -0,0 +1,18 @@
+# Generated by Django 3.0.3 on 2020-03-04 07:52
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('uncloud_vm', '0013_auto_20200303_1845'),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name='vmproduct',
+            name='vmid',
+            field=models.IntegerField(null=True),
+        ),
+    ]