HPCC-9277 Excessive tracing in lookupFileName

Make it conditional on traceLevel

Signed-off-by: Richard Chapman <rchapman@hpccsystems.com>
Merge pull request #4357 from richardkchapman/roxie-tracing

HPCC-9277 Excessive tracing in lookupFileName

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>