Remove LocalisationCache::unloadAll() call from NewParserTest::addDBData()

Remove LocalisationCache::unloadAll() call from NewParserTest::addDBData()

- Localisation cache does not depend on the database, only on the
  localisation files themselves
- the backend is already set to LCStore_Null, so it will not interfere
  with other caches (CDB, database, etc.)

Unloading the whole cache before each test thus only adds overhead
without any benefit, and slows down the test suite (this changes allows
to win about 20 seconds on my local machine).

Change-Id: Ifa36a7135d9f8355e1a10dd49ece806d90f657a2