Include ping6 in userdebug builds.

Also require that the user be root or have Internet
permission, like we do for IPv4.

Change-Id: I8ab8350885548ab83d5198adee912137b36d7a8d
Merge "Include ping6 in userdebug builds."
Merge tag 'android-4.3_r2.1' into jellybean-mr2.1

Android 4.3 release 2.1