Bug 9032: Unit tests for sharing lists

Bug 9032: Unit tests for sharing lists

This patch combines some work from bugs 10389 and 10441.
With thanks to Srdjan and Jonathan Druart for their contributions.

Adds tests for AddShare, AcceptShare, IsSharedList, RemoveShare.
This patch also restores the inadvertently deleted DelShelf tests
in bug 10499.

Test plan: Run the test VirtualShelves.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Dobrica Pavlinusic <dpavlin@rot13.org>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>