Small refactoring and bugfixes for the polkitAgent

Fix some bugs and usability issues in the polkit dialog:

  • Make the "Authenticate" button insensitive by default until polkit asks for a password
  • Make the "Authenticate" button insensitive if there's nothing in the password entry
  • Also show the avatar for the root user
  • Update the user name on user-changes
  • Set key focus to the "Cancel" button if there's no password entry
  • Fix a bug where the user avatar isn't visible on first run of the dialog

Merge request reports