Use UM.DISALLOW_OEM_UNLOCK instead of Global.OEM_UNLOCK_DISALLOWED

Currently we used global setting to restrict user from enabling oem
unlock. As global settings can be chagned using adb, using user
restrictions instead.

Bug: 29893399
Change-Id: Icaffb080979a447d1e0f7f0d72f92c9db83ac10c
1 file changed