Fix lock settings pattern crash on configuration change

A helper class used in LockPatternView.onSaveInstanceState() and
.onRestoreInstanceState() wasn't set, causing to NPE settings once
a configuration change would happen while displaying lock pattern
input.

This is now set on creation.

Test case:
1) Enable rotation on device.
2) Open Settings/ChooseLockPattern preference.
3) Rotate device

Change-Id: Ic8091bc92dee2a9a23f4ddebd6de4111ec8ac318