Trying to fix problem with shared database connection

This commit fixes problem, but brakes tests - SQLite3::BusyException:
database is locked: commit transaction

---

To reproduce problem:

start with fresh database/cache, or clear it:

    [Lit::Locale, Lit::Localization, Lit::LocalizationKey].map(&:delete_all)
    I18n.backend.cache.clear

try to save some record - it will have validation errors. I18n will try to
translate attribute names and Lit save this translations to DB (and in cache).

    SomeModelWithValidations.create

but because this record can't be saved AR rollback transaction (and all Lit
transaction/locales also). Now lit cache contains transactions/locales,
but they aren't exist in DB.

we can now try to translate some key:

    I18n.translate(:some_key) # => SystemStackError: stack level too deep

---

Another way to reproduce(without model involving):

    [Lit::Locale, Lit::Localization, Lit::LocalizationKey].map(&:delete_all)
    I18n.backend.cache.clear

    ActiveRecord::Base.transaction do
      I18n.t('not_existing_key', default: 'ok')
      raise ActiveRecord::Rollback
    end
    I18n.t('not_existing_key') # => 'ok'
    Lit::LocalizationKey.exists? # => false
    I18n.t('other_key') # => SystemStackError: stack level too deep