nfs: do not use CDC as try-with-resource

in a cunstruction like:

  try (CDC ignored = new CDC()) {
     ....
  } catch (Exception e) {
    log.error(e);
  }

the catch block will not have a correct context.
Use try-catch-finally instead.

Acked-by: Gerd Behrmann
Target: master, 2.9, 2.8, 2.7
Require-book: no
Require-notes: no