Set divider based on selectability rather than enabled

This matches how framework preferences work.

Change-Id: If75cf74481741bb442bfc4e1e20a0a026d3a6ebe
(cherry picked from commit 1520a6835986451fb8a97b9fdb02fd94ac537640)
diff --git a/v7/preference/src/android/support/v7/preference/Preference.java b/v7/preference/src/android/support/v7/preference/Preference.java
index 1460005..84ab3b3 100644
--- a/v7/preference/src/android/support/v7/preference/Preference.java
+++ b/v7/preference/src/android/support/v7/preference/Preference.java
@@ -517,8 +517,8 @@
             setEnabledStateOnViews(holder.itemView, true);
         }
 
-        holder.setDividerAllowedAbove(isEnabled());
-        holder.setDividerAllowedBelow(isEnabled());
+        holder.setDividerAllowedAbove(isSelectable());
+        holder.setDividerAllowedBelow(isSelectable());
     }
 
     /**