Lower carp demote count on interface detach, fixes a bug introduced by rev 1.175.
Lower carp demote count on interface detach, fixes a bug introduced by rev 1.175.

ok henning mpf

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars