HPCC-9467 Thor needs to provide user credentials

Running regression test multilfn.ecl results in UNEXPECTED USER error
in message sent from THOR to DALI. This fix ensures a populated user
descriptor is provided to the normalizeLFN method

Signed-off-by: William Whitehead <william.whitehead@lexisnexis.com>
Merge pull request #4478 from RussWhitehead/Unexp

HPCC-9467 Thor needs to provide user credentials

Reviewed-By: Jake Smith <jake.smith@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>