Add support for persist.sys.locale.

AndroidRuntime has been changed to read "ro.product.locale" and
"persist.sys.locale" instead of "ro.product.locale.language" etc.
This is passed down as "-Duser.locale" to the runtime.

The system_server has been changed to write out persist.sys.locale
on locale changes.

bug: 17691569

Change-Id: I93360c8795c9620a133656dc491d13d7b6ed162e