hadoop: fix meta.position

This was broken because the `recursiveUpdate` in the `meta` block causes
Nix to lose track of `meta.description`'s position.

pkgs/applications/networking/cluster/hadoop/default.nix

@@ -144,6 +144,8 @@ let
 
       passthru = { inherit tests; };
 
+      # The recursiveUpdate below breaks default meta.position, so manually override it.
+      pos = __curPos;
       meta =
         with lib;
         recursiveUpdate {