Bug 16860: Catch warning t/db_dependent/ClassSource.t

Bug 16860: Catch warning t/db_dependent/ClassSource.t

$ prove t/db_dependent/ClassSource.t
t/db_dependent/ClassSource.t .. 3/24 attempting to use non-existent class sorting routine routine1
t/db_dependent/ClassSource.t .. ok
All tests successful.
Files=1, Tests=24,  1 wallclock secs ( 0.02 usr  0.00 sys +  0.66 cusr  0.02 csys =  0.70 CPU)
Result: PASS

The above warning might be scary to those unfamiliar with the test.
Add a test to catch the warning.

TEST PLAN
---------
1) prove t/db_dependent/ClassSource.t
   -- as above
2) apply patch
3) prove t/db_dependent/ClassSource.t
   -- no message
4) prove -v t/db_dependent/ClassSource.t
   -- test 13 is the new test
5) run koha qa test tools

Signed-off-by: Hector Castro <hector.hecaxmmx@gmail.com>
Workas as advertised

Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit b80318f1b7441328d818dfe67a4cb8cd345f585e)
Signed-off-by: Frédéric Demians <f.demians@tamil.fr>