Clean up some resources and change switch-case to if-else block.

Preparatory CL for upcoming shared lib change.

Test: basic sanity
Bug: 144806641
Change-Id: I8f81195b72c6329844a450ce28d76f949f41e2d8
diff --git a/res/xml/voicemail_settings.xml b/res/xml/voicemail_settings.xml
index 021a764..cbe1cf4 100644
--- a/res/xml/voicemail_settings.xml
+++ b/res/xml/voicemail_settings.xml
@@ -15,7 +15,7 @@
 -->
 
 <PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android"
-    xmlns:phone="http://schemas.android.com/apk/res/com.android.phone"
+    xmlns:phone="http://schemas.android.com/apk/res-auto"
     android:title="@string/voicemail">
 
     <com.android.phone.settings.VoicemailProviderListPreference