crontabberise drop_old_partitions; bug 1014128; attempt #2

This addresses bug 1014128. Again. (Previous attempt at rebasing was a horrible disaster. :unamused:) 

`?r` @peterbe and/or @rhelmer :revolving_hearts: 
It's not really that important right here because this is a test and has no user data to be worried about but the correct way of doing this would be:
```
        statement = """
        CREATE TABLE %s();
        INSERT INTO report_partition_info (table_name, partition_column,
        timetype) VALUES ('%%s', 'date_processed', 'TIMESTAMPTZ');
        """ % (TABLE,)
        cur.execute(statement, (TABID,))
```
Does that make sense?