At the time of entering username and password in browsers, most of the browsers ask us to save the password.
Removing AutoComplete was part of Enhancement ID 599021 due to the security aspect involved in saving passwords in the browsers.

So from 11.1, changes have been done in client piece code so that browsers would not pre-fill the username/password fields with saved credentials.

This is expected behavior and unfortunately there is no option to allow AutoComplete in 11.1.