HPCC-11901 CSV auto discovery generates wrong field names if
recordstructurepresent=false

Fix record structure generation.

Signed-off-by: Attila Vamos <attila.vamos@gmail.com>
Merge pull request #6232 from AttilaVamos/HPCC-11901-fix

HPCC-11901 CSV auto discovery generates wrong field names if recordstructurepresent=false

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>