xapi_sm: Don't allow host_pending_features that are empty

When none on of the hosts have pending features, a map was produced with
all the hosts with an empty value for each after upgrading. Empty the
map instead when that occurs.

Signed-off-by: Pau Ruiz Safont <pau.safont@vates.tech>

Author: psafont

ocaml/xapi/xapi_sm.ml

@@ -95,6 +95,12 @@ let remove_valid_features_from_pending ~__context ~self valid_features =
         (h, Listext.List.set_difference pending_features valid_features)
     )
   in
+  let new_pending_feature =
+    if List.for_all (fun (_, v) -> v = []) new_pending_feature then
+      []
+    else
+      new_pending_feature
+  in
   Db.SM.set_host_pending_features ~__context ~self ~value:new_pending_feature
 
 let update_from_query_result ~__context (self, r) q_result =