HPCC-11663 - Cannot upload a file if landing zone is empty

The overwrite flag was the only way to upload a file if the landing zone was empty. Fixes HPCC-11663.

Signed-off by: Miguel Vazquez <miguel.vazquez@lexisnexis.com>
Merge pull request #6054 from miguelvazq/HPCC-11663

HPCC-11663 - Cannot upload a file if landing zone is empty

Reviewed-By: Gordon Smith <gordon.smith@lexisnexis.com>