When we trigger post notification sending we used to create post notification history record,
save all scheduled task subscribers but didn't update counts on queue.
Counts were eventually updated when sending started. This was causing some issues e.g. when sending
got stuck post notification item was showing 0/0 in sending status.
Pausing/resuming such a post notification caused that it was immediately set as sent.
This commit adds updating counts in queue immediately when sending starts.
[MAILPOET-3962]
6f5cde2fbf