default screensaver/locker settings

[Jonathan Riddell]

The screensaver was changed a couple of KDE SC releases ago to default
to a locker instead of a screensaver.  Upstream has it off entirely by
default but if you enable it then it defaults to the lock UI but
without actually needing a password which makes it look like it is
broken to me. In kubuntu-settings-desktop we currently enable it by
default but don't require a password.

Which should we change it to? disable it entirely (upstream default)
or enable it and require a password after 300 seconds of showing (more
secure but might get in the way of watching flash or vlc where it
doesn't add fake keystrokes when playing)?

Jonathan