Schedule all runs for recurrent reports through scheduler

To allow coalescing reports, the first run of a recurrent report was
scheduled immediately outside of the scheduler.

Besides buying us two different ways recurrent reports got injected,
it made us jump through hoops to test that the first run was executed,
and it injected stale, unrequested data into the report.

By making the parent report coalescable without recurrent reports, we
get rid of all the above three issues.

Now all recurrent runs (also the first one) get scheduled in the same
way. This unified scheduling considerably simplifies follow-up commits
that will postpone recurrent runs if the replication lag is too high.

Change-Id: I5d671e85ddd96fa9239a16f86e84a92fde00ffed