theme: login-dialog-timed-login-indicator fixes

First commit fixes wrong color used in .login-dialog-timed-login-indicator that was added in 11965324.

Other commits attempt to further improve and clean-up the timed-login-indicator styling, by merging duplicate style declarations, and always using the same color.

Before/after screenshots of the timed-login-indicator, when user-list is disabled:

before	after

There's no change to the appearance of the indicator inside the user-list-item.

EDIT: The above screenshots are slightly outdated: Current revision doesn't change the spacing between the login entry, and the timed-login indicator.