Added the error ER_NOT_SINGLE_ELEMENT_ORDER_LIST for th percentile functions, these ensure that for the percentile function we have the order list with exactly one element
Added the error ER_NOT_SINGLE_ELEMENT_ORDER_LIST for th percentile functions, these ensure that for the percentile
function we have the order list with exactly one element

natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2,natsys/mariadb_10.2