Bug 14570: Handle missing 'relationship' in atomicupdate (bad data)

Bug 14570: Handle missing 'relationship' in atomicupdate (bad data)

This patch adds two steps to the upgrade process:
- Handle the pathologic case in which there's a guarantorid and no
'relationship'.
- Performs a cleanup on the relevant columns when the guarantor data
contains a guarantorid, and is then migrated into the
borrower_relationships table. The original code left the information
in the borrowers table, so no clear separation between guarantors as
patrons and the virtual ones.

Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>