fix host_db extraction for sqlite3

Fixes `Resolver#connection_url_to_hash`,

```ruby
Before
 'sqlite3://foo:bar@dburl:9000/foo_test?encoding=utf8' # => database: '/foo_test'

After
 'sqlite3://foo:bar@dburl:9000/foo_test?encoding=utf8' # => database: 'foo_test'
```