HPCC-12213 Revise based on review comments

1. Remove the extra c in totalCcolumnCount;
2. Add a comment for the error check;
3. Move the nameStr to the {} block;
4. Remove the IDFUFileMetaDataReader;
5. Change the Owned<IDFUFileMetaDataReader> dataReader
     = new CDFUFileMetaDataReader(...);
   to: DFUFileMetaDataReader dataReader(...).

Signed-off-by: wangkx <kevin.wang@lexisnexis.com>