Bug 16176: Fix a test about OpenLibrarySearch

 Bug 16176: Fix a test about OpenLibrarySearch

Introduced by bug 6624: When C4::UsageStats::BuildReport is modified,
the tests should be too.

Test plan:
  prove t/db_dependent/UsageStats.t
should return green

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Note that if we maintain this list of sysprefs at two places, we will
probably have this test failing regularly..

Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>