Bug 18014: Add test to AuthoritiesMarc.t to expose problem in AddAuthority

Bug 18014: Add test to AuthoritiesMarc.t to expose problem in AddAuthority

Since AddAuthority uses max(id)+1 logic to produce the next authid,
authority id's will be reused when you delete the last record. This may
be a source of problems and will be addressed on the next patch.

This patch add a test to expose the problem.

Test plan:
[1] Run t/db_dependent/AuthoritiesMarc.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>