init.tuna.rc: enable sandboxing for rild

Sandboxing the rild forecloses the possibility of remote access to files
on the phone through the cellular baseband, as described in
http://redmine.replicant.us/projects/replicant/wiki/SamsungGalaxyBackdoor
.

Change-Id: I7e852de29435ae3ec9b8d0d75a18bc1fa337507a
Signed-off-by: Dan Trifan <jimsth@gmail.com>