Old jobs were queued with array( $userId => $userId ), so there will be no
'0' index. Use array_values() since we don't care about the keys.
Change-Id: I1155d310c7fa09c728797d35d63c7cec0383511c
EchoNotificationDeleteJob now only processes one user at a time. If
given multiple user ids, it will queue individual jobs for each user id
rather than processing many at once.
Bug: T102574
Change-Id: I627f059280d8fab3854d9ca8417f22179478772c
