Bug 19487: Fix MarkIssueReturned.t

Bug 19487: Fix MarkIssueReturned.t

MarkIssueReturned must now return directly if the issue does not exist.
We then check if the anonymous patron configuration is correct.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
(cherry picked from commit 60bb936bc28b73f1653207cce36f432dec094017)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>
(cherry picked from commit 49beda21761e57d1d7b389e6a08f3327a53215b0)
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>