Bug 6657: Prevent biblionumber to be duplicated

Bug 6657: Prevent biblionumber to be duplicated

If the biblionumber field is displayed in the framework, on editing a
biblio the field/subfield will be duplicated.
To prevent that this patch adds a check when building the field list.

Test plan:
1/ map biblio.biblionumber with 999$c
2/ Display 999$c in a framework
3/ Edit a biblio using this framework
4/ Save => The field should not have been duplicated

5/ map biblio.biblionumber with 001
6/ Display 001 in a framework
7/ Edit a biblio using this framework
8/ Save => The field should not have been duplicated

Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Works as described, aldo removes duplicate values.
No errors

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>