Bug 17638: Make sure t/db_dependent/Search.t doesn't use a cached koha-conf.xml

Bug 17638: Make sure t/db_dependent/Search.t doesn't use a cached koha-conf.xml

This patch makes the tests clean the 'config' namespace for cache before
it runs any tests.

To test:
- Run:
  $ prove t/db_dependent/Search.t
=> FAIL: Self explanatory
- Apply the patch
- Run:
  $ prove t/db_dependent/Search.t
=> SUCCESS: All green
- Sign off :-D

Signed-off-by: Hector Castro <hector.hecaxmmx@gmail.com>
All test pass successfuly

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Cannot reproduce, but I trust everyone telling me it's failing ; )
No regressions spotted