adbd: Disable "adb root" by system property (2/3)

 * Require persist.sys.root_access=1 on non-eng debuggable builds

Change-Id: Iedab030e81ffb525fed64aed80cf0014f3e07073
Update permissions to the superuser binary

Change-Id: Ia382c74854cfbe625653b8b6b016b37f93132658
Import Superuser init.rc