fix(Auth): authenticate with any password for default user

[kostasrim]

Address #1862

Basically, our implementation would only verify the default user with the password nopass. This restriction is lifted and now we conform with the redis impl of AUTH that authenticates with any password.

Moreover, I should check in a separate PR:

Otherwise if the "default" user is not flagged with "nopass"
# the connections will start in not authenticated state, and will require
# AUTH (or the HELLO command AUTH option) in order to be authenticated and
# start to work.