[ML] Fix master node deadlock during ML daily maintenance#31691

Merged

jasontedor merged 2 commits intoelastic:6.3from

davidkyle:daily-maintenance-tp-fix

Jun 29, 2018

Commits on Jun 29, 2018

ML expired data cleanup cannot run on the client thread
davidkyle
committed
Remove redundant assertions and comment on the importance of using the correct thread pool
davidkyle
committed