androidfw: Use the last package to create idmap.

 - If the resource only contains one namespace, then need to use the first
   index 0 to create idmap.
 - If the resource contains two namespaces. Then the first package is the
   system package, the second package is the application package. So need
   to use the last index 1 to create the idmap.

Change-Id: I34b72684f82dfc740a5f44762eec55b5e5b3f902