Bad error handling in mysql_admin_table for partitioned tables.

Instead of returning error, mysql_admin_table produces a result-set
which includes the error message and returns OK.

Adjusted error handling for partitioning accordingly.

Reviewed-by: Praveen Hulakund <praveenkumar.hulakund@oracle.com>
Reviewed-by: Debarun Banerjee <debarun.banerjee@oracle.com>
RB: 8467