Fix db upgrade for the scrubber
This MR consists in 2 revisions:
-
fix the 5->6 upgrade sql script
Need to drop the index of the old checked_partition before recreating the new one (with the same name); simplest way of doing this is cascade droping the old checked_partition table before recreating the new index.
-
Rename the 'scrubber_db' config section as 'scrubber'
This is needed to make it compatible with swh.core's db upgrade tooling: the name of the configuration section is exptected to be the swh module.