doc: bulk insert using select *

In https://mariadb.com/kb/en/library/columnstore-bulk-data-loading/, we have an example of how to do a select from a table into cpimport. The example doesn't work.

mcsmysql -q -e 'select * from source_table;' -N db2 |
/usr/local/mariadb/columnstore/cpimport -j501 -s '\t' -f STDIN

-j501 is telling it to use a jobfile, but there's no colxml job described.

If you replace -j501 with database and table positional parameters, you need to remove the -f STDIN, and the user must have write permissions to /usr/local/mariadb/columnstore/data/bulk/tmpjob/