HBSD: Use a SYSINIT for prison0 to satisfy one of Robert Watson's (rwatson@) concerns

(cherry picked from commit 3d205f614c245af4e10ced4e12b0fd89919d4a5a)
Signed-off-by: Oliver Pinter <op@hardenedbsd.org>
HBSD: user strlcpy in prison0_init

Signed-off-by: Oliver Pinter <oliver.pntr@gmail.com>