Propagate ROLLBACK_REQ from parent to chilren tasks
When task controller child is terminated, decrease both unfinishedChildren & unvalidatedChildren.
The idea of the fix is the same as the one documented in commit 0ba5c2f44951472dc0a838edfb0cf4c9950dcdbf
Children should start commit at the same time parent task does it.
Thus moving SEND_COMMIT_REQ from COMMIT_WAIT to COMMIT phase.