Bug 5161: Keep patron's attributes on warning/duplicate

Bug 5161: Keep patron's attributes on warning/duplicate

When a patron is added or modified and a warning appears (duplicate,
inconsistent data, etc.) the form lost the patron's attributes.

Test plan:
Create some attribute types for patrons
Create a new patron, use an userid that already exists and fill the attributes
=> You get a warning and the attributes are kept
Modify the userid and save again
Edit the same patron
Modify the attributes, as well as the userid (to get the duplicate warning)
=> You get a warning and the attributes are kept with the modified
values
Modify the userid and save again
=> The new values are saved
Edit the attributes from the detail page (so not with the full edit form)
Modify them and save
=> The new values are saved

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>