bhyve: change suspend exit code

[novel]

Summary

Currently, after suspending, bhyve(8) exits with 0. This code is
also used to indicate that a VM was rebooted. To differentiate
reboot and suspend, use the next available exit code, 5, for suspend.

[markj]

usr.sbin/bhyve/snapshot.c

1311

@bnovkov this will require an update in D53730.

[bnovkov]

usr.sbin/bhyve/snapshot.c

1311

Thanks, I've updated the diff before landing the commits.