Check already_joined in verify_tried_joining

Second way of checking join status for each table:
just ask get_server directly

Useful, if remote node sends us cancel_check

src/cets_discovery.erl

@@ -595,7 +595,9 @@ verify_tried_joining(State = #{nodes := Nodes, tables := Tables}) ->
     NodesToJoin = [Node || Node <- Nodes, lists:member(Node, AvailableNodes)],
     Missing = [
         {Node, Table}
-     || Node <- NodesToJoin, Table <- Tables, not has_join_result_for(Node, Table, State)
+     || Node <- NodesToJoin,
+        Table <- Tables,
+        not (has_join_result_for(Node, Table, State) orelse already_joined(Node, Table))
     ],
     case Missing of
         [] -> [];
@@ -606,6 +608,18 @@ verify_tried_joining(State = #{nodes := Nodes, tables := Tables}) ->
 has_join_result_for(Node, Table, #{results := Results}) ->
     [] =/= [R || R = #{node := N, table := T} <- Results, N =:= Node, T =:= Table].
 
+-spec already_joined(node(), cets:table_name()) -> boolean().
+already_joined(Node, Table) ->
+    lists:member(
+        Node,
+        try
+            %% Careful, it is a blocking call
+            cets:other_nodes(Table)
+        catch
+            _:_ -> []
+        end
+    ).
+
 -spec handle_system_info(state()) -> system_info().
 handle_system_info(State) ->
     State#{