In `WP_Terms_List_Table::single_row()`, call `sanitize_term()` on the passed term (`$tag`).

Props oso96_2000, c3mdigital, scribu. 
It takes a village.
Fixes #16864.


git-svn-id: https://develop.svn.wordpress.org/trunk@28360 602fd350-edb4-49c9-b593-d223f7449a82