Bug 11287: make patron import tool take new restrictions system into account

The import patrons tool will add restrictions in the previous style (
directly to the borrowers table ). This will actually work, but
will result in the restriction being un-removable, and will be
overwritten by any new restrictions.

Test Plan:
1) Apply this patch
2) Import new patrons with debarrments, note the debarment is created
   correctly
3) Import existing patrons with overwrite enabled, note that any new
   debarrment is added, and any existing debarrment is ignored

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>