Bug 15682 - Only allow merging of 2 or more records form lsits (for consistency)

Bug 15682 - Only allow merging of 2 or more records form lsits (for consistency)

Test as above but on shelves.pl

Signed-off-by: Chris Cormack <chrisc@catalyst.net.z>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Brendan Gallagher <bredan@bywatersolutions.com>
(cherry picked from commit 9550e37fc66402500adf8bca7a1c90ee0104cdd0)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
(cherry picked from commit 9f1e23735f46a8b014d4a8983796f1b8b37cc9b4)
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>