Display the correct encryption settings.

* You can no longer try to encrypt the device when it is encrypted.
* Moved the encryption section below the lock screen section. It will be more common to change the lock screen settings.
* If the device doesn't support encryption don't display the encryption section.

Bug: 3384074
Change-Id: I172f5894a3cea57b1b8d03a84f1ecf0ee500c1f3