init: allow system UID to setenforce and set booleans

Allow system UID to setenforce and set booleans for SELinux.
Boolean ownerships must also be reset upon policy reload as
the boolean files in selinuxfs are regenerated to match the new policy.

Signed-off-by: Humberto Borba <humberos@gmail.com>
Change-Id: I0dae393892753b4745e6c956289196338bf771d5