Bug 16819: Unit tests for C4::Members::DelMember

Bug 16819: Unit tests for C4::Members::DelMember

The C4::Members::DelMember function actually deletes reserves, and it is
not properly tested.

To test:
- Apply the patch
- Run:
  $ prove  t/db_dependent/Members.t
=> SUCCESS: Tests pass
- Sign off

Sponsored-by: NEKLS
Signed-off-by: Hector Castro <hector.hecaxmmx@gmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit 13bf3686c5d0fd3a3a192db961118535ece41a4c)
Signed-off-by: Frédéric Demians <f.demians@tamil.fr>