further cleanup of LockscreenSecuritySettings

*) remove owner information, it can be already found at Security Settings
*) always load delay preferences if lockscreen is enabled
*) remove power button instantly locks, as the same can be achieved with
the listpreference of the load delay preferences
*) remove isCmSecurity check. we do not need it as its a seperate fragment
*) remove unused variables

Change-Id: Id0229a313231af734ecd7e3a7dbae851c07ea8d4