Bug 19513: More changes to MarkIssueReturned.t (after bug 19487)

Bug 19513: More changes to MarkIssueReturned.t (after bug 19487)

This patch was initially created as QA follow-up on 19487.

$dbh is not used
$categorycode is no longer used
%item_branch_infos not used
$borrowernumber is obsoleted by using $patron
No real need for $anonymous_borrowernumber (Since MarkIssueReturned returns
undef rightaway for an invalid itemnumber, the privacy stuff is irrelevant.)
No AddMember calls, removing unneeded modules

Adding a test that calls MarkIssueReturned on an item already returned.

Test plan:
[1] Run t/db_dependent/Circulation/MarkIssueReturned.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>