From COMPASS-745, it looks like Kerberos and X.509 are also likely to double-encode their auth-component in the same way LDAP does.

This ticket should:

1. Confirm if this is true, e.g. with https://docs.mongodb.com/v3.2/tutorial/control-access-to-mongodb-with-kerberos-authentication/

2. If so, add a regression test in connection-model.
3. Remove all redundant encodeURIComponent calls, including in comments to make it clearer that url.format already handles this even better than we could (git blame reveals it has been optimised for more performance).