Allow AID_RADIO to restart the ril-daemon.

This enhances robustness by allowing the Telephony Framework to restart
ril-daemon if it notices some catastrophic failure.

Added setprop ctl.restart.
Added ril-daemon to setprop control_perms and allow users/groups
with the AID_RADIO ID to control it.

Change-Id: I195abdd754a731ce0b77e8f71ab47fde8c3e7977