Use device protected storage

Switch from using shared preferences, which aren't available during
boot, to device protected storage, which is. This is required since
the RotaryService is directBootAware.

Bug: 166354638
Test: manual
Change-Id: Ia72e4b96b279041e1cd7d1c3f9cfa151044183ce
diff --git a/src/com/android/car/rotary/RotaryService.java b/src/com/android/car/rotary/RotaryService.java
index 9fd5d14..f340df2 100644
--- a/src/com/android/car/rotary/RotaryService.java
+++ b/src/com/android/car/rotary/RotaryService.java
@@ -406,7 +406,8 @@
                 hunRight,
                 showHunOnBottom);
 
-        mPrefs = getSharedPreferences(SHARED_PREFS, Context.MODE_PRIVATE);
+        mPrefs = createDeviceProtectedStorageContext().getSharedPreferences(SHARED_PREFS,
+                Context.MODE_PRIVATE);
         mUserManager = getSystemService(UserManager.class);
         mTouchInputMethod = mPrefs.getString(
                 TOUCH_INPUT_METHOD_PREFIX + mUserManager.getUserName(),