Created attachment 13095 [details] [review]
Patron's dateexpiry is erroneously updated if dateexpiry in UnWantedField syspref

If dateexpiry field is absent from patron page because it has been included in
UnWantedField syspref list, the script normally assumes that the date has
been forgotten and update it by default when clicking on 'save' button.
But you may have to make a data modification (add for example a note about overdue items to a patron which dateexpiry is expired ) on a patron's file without changing the dateexpiry. This patch makes it possible.

Test plan :
1) add dateexpiry in UnWantedField syspref
2) choose a patron that have for example an expired dateexpiry
3) Click Edit button and make a modification
4) Save

Before the patch, the date is renewed according to the date or period attached to the patron category.
After, it does not.