This is better implemented as a separate set of extension to the local
authority. The only current known user, PolkitLockButton, will be
ported away from using these interfaces.

Since polkit still hasn't reached 1.0 this removal of functionality is
OK especially since the NEWS file has already wanred something like
this may happen.

Signed-off-by: David Zeuthen <davidz@redhat.com>