Bug 27857: Move extended_attributes tests to Koha/Patron.t

Bug 27857: Move extended_attributes tests to Koha/Patron.t

They really belong here. both Patron.t and Patrons.t got lengthy and it
is not intuitive to look for tests for a Koha::Patron method in the
Patrons.t file.

To test:
1. Run:
   $ kshell
  k$ prove t/db_dependent/Koha/Patron.t \
           t/db_dependent/Koha/Patrons.t
=> SUCCESS: Tests pass!
2. Apply this patch
3. Repeat 1
=> SUCCESS: Tests still pass, no new stuff
4. Sign off :-D

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>