Stop extraneous report runs for parent of recurrent reports

When creating a recurrent report, the parent run itself first
computed a report with data from today 00:00 until now. This report
got stored with the current date as filename. Afterwards the parent
run scheduled a first recurrent report run for data from yesterday
00:00 until today 00:00. This second run also got stored with the same
current date as filename.

By both reports using the same filename, the parent run's data
immediately got overwritten by the first child's run. This takes place
before the first coalesced report get generated. Hence, the data
computation for the parent run is unnecessary, and only wastes
resources.  So we drop the data computation step from the parent run,
as it would also get in the way when we implement replication lag
dependent recurrent report runs in follow-up commits.

Change-Id: Ib4a000288de506a32b2cf4c16e72d7dc35af572a