db options does not fire select db on createClient when url (with specified db number) is provided

• Version: 2.8.0
• Platform: Node JS 12.8.0 on MacOS Mojave 10.14.5
• Description:
  as the title said, I expect when the db option is provided, it will fire select command on connect using the db option provided regardless whether url provides db number or not.

How to reproduce:

const redis = require('redis')
const url = 'redis://127.0.0.1:6379/0'
const client = redis.createClient({db: 3, url: url})
client.selected_db // this will return 0, instead of 3 which I expect
client.set('foo', 'bar') // upon checking on redis-cli this is written to db 0, not on db 3

Start at the createClient option handling for the URL and db settings, then reproduce the provided Node.js example with Redis. Done means a client created with db: 3 selects database 3 even when the URL contains /0, and writes from client.set go to database 3.