[misc] Bulletproofing and log

(cherry picked from commit 1d6c5dbc082272463b32d3df9d4a0c7417863baf)
XWIKI-10144: Scheduler job displayer should use groovy hinghlight instead of java one

(cherry picked from commit 9d422b9fe4c3bded49bc1e34649b38bd59decf84)