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: 
Use `eq_(result[0], 1)` instead. 

And at the top of the file you need to do `from nose.tools import eq_`. See some of the other files in the same directory.