CA-415952: HA can not be enabled (xapi-project#6625)

xenserver/xha@7ed46d6
Add a new field *HostIndex* into the ha_query_liveset result, Xapi needs
to update accordingly to parse the result, Otherwise, xapi can not parse
the result and understand the liveset thus cause pool-ha-enable always
failed

This commit fix the issue and intend to be compatible with old/new xha,
to update smoothly

Author: liulinC

ocaml/xapi/xha_interface.ml

@@ -493,7 +493,7 @@ module LiveSetInformation = struct
         ( match first_xml_element_with_name elements "localhost" with
         | Some
             (Xml.Element
-              (_, _, [Xml.Element ("HostID", _, [Xml.PCData local_host_id])])
+              (_, _, Xml.Element ("HostID", _, [Xml.PCData local_host_id]) :: _)
               ) -> (
           match Uuidx.of_string local_host_id with
           | None ->