Add HA group consideration

[pin-chen]

• It is possible to be migrated to a machine outside of the HA group and then migrated back due to HA, causing errors.
• Add an HA group check during migration candidate generation. Nodes not in the same HA group should not be considered.

[kjj2]

This fails if you have any VMs that aren't assigned to a group in HA. Simple fix:

@@ -255,6 +255,8 @@
         for item in temp:
             if item['type'] != 'service':
                 continue
+            if "group" not in item:
+                continue

             # sid example: vm:134
             vm_id = int(item['sid'].split(':')[1])