Add a simple chroot jail wrapper 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: Iad069678097859153c1b7c56ab57e1c9efdb550d
Signed-off-by: Dan Trifan <jimsth@gmail.com>
Merge "Add a simple chroot jail wrapper for rild" into kk44