Bug 17909: Adding tests from bug 11315

Bug 17909: Adding tests from bug 11315

Based on original patch from Maxime Beaulieu on bug 11315.
Amended by Marcel de Rooy on report 17909.

EDIT:

Original tests have been adjusted in view of:
[1] Test on bug 11315 heavily leaned on DBD::Mock. Since we are
    using Test::DBIx::Class on such tests now, this would need attention.
    Moreover, the advantage of mocking the database in this case is at
    least arguable.
[2] Matching the first (somewhat older) subtest of 11700.
[3] Simplification and readability.
    Look e.g. at the use of $MARCto and $MARCfrom on 11315.

This made me merge them in the db_dependent counterpart.

Also note that this subtest adds another needed test case: the merge from
auth1 to modified auth1, while 11700 tested auth1 to auth2.

Test plan:
Just run t/db_dependent/Authorities/Merge.t

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>