Bug 30933: (follow-up) Consolidate transfer checks

Bug 30933: (follow-up) Consolidate transfer checks

Adding shelf->cannot_be_transferred with unit tests.

Note: This follow-up actually refers to comment42 on the
preceding report 25498.
Furthermore, we could still improve later on using error code
more effectively (adding codes). Here we concentrate on moving
the checks to module level.

Test plan:
Run t/db_dependent/Virtualshelves.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>