mirrored_supervisor: Catch timeout from Khepri in hanlde_info/2

[Why]
The code assumed that the transaction would always succeed. It was kind
of the case with Mnesia because it would throw an exception if it
failed.

Khepri returns an error instead. The code has to handle it. In
particular, we see timeouts in CI and before this patch, they caused a
crash because the list comprehension was asked to work on a tuple.

[How]
We now retry a few times for 10 seconds.

deps/rabbit/src/mirrored_supervisor.erl

@@ -345,7 +345,7 @@ handle_info({'DOWN', _Ref, process, Pid, _Reason},
                            child_order = ChildOrder}) ->
     %% No guarantee pg will have received the DOWN before us.
     R = case lists:sort(pg:get_members(Group)) -- [Pid] of
-            [O | _] -> ChildSpecs = update_all(O, Pid),
+            [O | _] -> ChildSpecs = retry_update_all(O, Pid),
                        [start(Delegate, ChildSpec)
                         || ChildSpec <- restore_child_order(ChildSpecs,
                                                             ChildOrder)];
@@ -428,6 +428,22 @@ check_stop(Group, Delegate, Id) ->
 
 id({Id, _, _, _, _, _}) -> Id.
 
+retry_update_all(O, Pid) ->
+    retry_update_all(O, Pid, 10000).
+
+retry_update_all(O, Pid, TimeLeft) when TimeLeft > 0 ->
+    case update_all(O, Pid) of
+        List when is_list(List) ->
+            List;
+        {error, timeout} ->
+            Sleep = 200,
+            TimeLeft1 = TimeLeft - Sleep,
+            timer:sleep(Sleep),
+            retry_update_all(O, Pid, TimeLeft1)
+    end;
+retry_update_all(O, Pid, _TimeLeft) ->
+    update_all(O, Pid).
+
 update_all(Overall, OldOverall) ->
     rabbit_db_msup:update_all(Overall, OldOverall).