Allow update_verifier to reboot the device

Currently update_verifier only verifies the blocks when dm-verity is in
'enforcing' mode; and dm-verity will reboot the device upon detection of
errors. However, sometimes the verity mode is not guaranteed to be
correct. When mode is 'eio' for example, dm-verity will not trigger
a reboot but rather fail the read. So update_verifier need to take the
responsibility to reboot the device. Otherwise the device will continue
to boot without setting the flag "isSlotMarkedSuccessful".

Denial message:
update_verifier: type=1400 audit(0.0:18): avc: denied { write } for
name="property_service" dev="tmpfs" ino=14678 scontext=u:r:update_verifier:s0
tcontext=u:object_r:property_socket:s0 tclass=sock_file permissive=0

Bug: 36260064
Test: powerctl property sets successfully
Change-Id: I7431f87e2d61be1425397732aebb369d4ad4c26c