fix(rpc): Follow-up to the previous fix

Author: ieQu1

src/mria_status.erl

@@ -86,7 +86,12 @@ start_link() ->
 %% as compared with `get_core_node'.
 -spec upstream_node(mria_rlog:shard(), timeout()) -> {ok, node()} | timeout.
 upstream_node(Shard, Timeout) ->
-    optvar:read(?optvar({?core_node, Shard}), Timeout).
+    case optvar:read(?optvar({?upstream_pid, Shard}), Timeout) of
+        {ok, Pid} ->
+            {ok, node(Pid)};
+        timeout ->
+            timeout
+    end.
 
 %% @doc Return pid of the core node agent that serves us.
 -spec upstream(mria_rlog:shard()) -> {ok, pid()} | disconnected.