[ticket/11547] Set MySQL charset to UTF8 in database_test_connection_manager.

PHPBB3-11547
[ticket/11542] Use Czech as example as it contains non-latin characters

PHPBB3-11542
Merge remote-tracking branch 'nickvergessen/ticket/11542-2' into develop-olympus

* nickvergessen/ticket/11542-2:
  [ticket/11542] Use Czech as example as it contains non-latin characters
Merge remote-tracking branch 'bantu/ticket/11547' into develop-olympus

* bantu/ticket/11547:
  [ticket/11547] Set MySQL charset to UTF8 in database_test_connection_manager.