Bug 12048: add regression test

This patch adds a regression test for verifying that superlibrarians
can see all subscription when IndependentBranches is on.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit 9af0aa288c23a6722333adebba7b8b3e12ed78e2)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
Bug 12048: restore ability of superlibrarian to see other libraries' subscriptions

This patch fixes a regression in master and 3.14. When a user has
superlibrian permissions, a search on serials subscriptions should
display other libraries' subscriptions even when IndependentBranches
syspref is enabled.

To reproduce/test the bug/patch:

1. Enable IndependentBranches (i.e. 'Prevent' staff...)
2. Login as a user not having superlibrarian permission
3. Search for a serial subscription on:
   /cgi-bin/koha/serials/serials-search.pl
4. Search a title which has at least 2 subscriptions: one in the user
   branch, and one in another branch
5. On the result page, just 1 subscription is displayed: the one
   attached to the userbranch
   => this is normal
6. Login as a user having superlibrarian permission
7. Repeat step 3-5.
8. You get the same result as 5. You should have seen all subscriptions.
   That's what you get after applying this patch.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>

NOTE: I tested a variation. My superlibrarian was a branch that
      was not the same as the non-superlibrarian. The serial was
      the same branch as the non-superlibrarian. Without the
      patch, the superlibrarian saw nothing, with the patch it
      saw the serial as expected.
      Also, remember the superserials permission can affect the
      results. I successfully changed the branch of the
      subscription, and then it ceased to show up with
      superserials not granted to the non-superlibrarian.
      I corrected the system preference name in the text here.

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Superlibrarian permission now allows to see all subscriptions
independent from the branch.
Passes all tests and QA script.

But the superserials permission appears broken to me before
and after this patch. If I have superserials - the search
doesn't show all subscriptions. If I don't have superserials
I can still edit any subscription accessing the subscription
detail page through the serial collection page or accessing
the detail page directly by manipulating the URL.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit 214d6b8d13c553027c868a00a2dd6b313f56608b)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>