Tweak spacing for horizontal preferences.

- Add minHeight to horizontal preference so they are not clustered
together.
- Wrap app_data_usage's into different categories so they don't rely on
SpacePreference to draw space and dividers.

Change-Id: Ieed90a39d48494d1207680483968b5733bdfb344
Fix: 37750568
Test: visual

res/layout/horizontal_preference.xml

@@ -16,11 +16,12 @@
 -->
 
 
-<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
+    android:minHeight="?android:attr/listPreferredItemHeightSmall"
     android:orientation="horizontal"
-    android:paddingTop="1dp"
     android:paddingStart="@dimen/preference_no_icon_padding_start"
     android:paddingEnd="?android:attr/listPreferredItemPaddingEnd">