Remove duplicate code for DECIMAL to int64_t rounding conversion

        case execplan::CalpontSystemCatalog::DECIMAL:

        case execplan::CalpontSystemCatalog::UDECIMAL:

        {

            IDB_Decimal d = parm[0]->data()->getDecimalVal(row, isNull);

            if (parm[0]->data()->resultType().colWidth == datatypes::MAXDECIMALWIDTH)

            {

                return static_cast<int64_t>(d.getPosNegRoundedIntegralPart(4));

            }

            else

            {

                double dscale = d.scale;

                int64_t value = d.value / pow(10.0, dscale);

                int lefto = (d.value - value * pow(10.0, dscale)) / pow(10.0, dscale - 1);

                if ( value >= 0 && lefto > 4 )

                    value++;

                if ( value < 0 && lefto < -4 )

                    value--;

                return value;

            }

        }