HPCC-11816 Fix regression introduced by HPCC-11571

logical filenames with cluster postfix's, e.g. file@cluster
were being incorrectly passed by CDfsLogicalFileName

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>
Merge pull request #6163 from jakesmith/hpcc-11816

HPCC-11816 Fix regression introduced by HPCC-11571

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>