In fff5923686c21dd147bde62d08e9f1042deadb4f all occurences of
users.extraUsers and users.extraGroups have been changed tree-wide to
users.users and users.group. In the meantime the hadoop modules were
introduced via #41381 (060a98e9f4ad879492e48d63e887b0b6db26299e).
Unfortunately those modules still use users.extraUsers, which has been
renamed a long time ago (14321ae2431e33f5ed81f1ee43eddd29c7e9d01d, about
three years from now), so let's actually rename it accordingly as well.
Signed-off-by: aszlig <aszlig@nix.build>
Cc: @matthewbauer, @aespinosa
