HPCC-11236 Non Dlls should not be registered with the dllserver

Signed-off-by: Gavin Halliday <gavin.halliday@lexisnexis.com>
Merge pull request #5703 from ghalliday/issue11236

HPCC-11236 Non Dlls should not be registered with the dllserver

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>