dhclient-script: s/addr add/addr replace/
It might happen that the address is already there,
in which case we want to update life-times.
BZ#1187856#c15
ip addr add = NLM_F_CREATE|NLM_F_EXCL
ip addr replace = NLM_F_CREATE|NLM_F_REPLACE
ip addr change = NLM_F_REPLACE
from linux/netlink.h
NLM_F_REPLACE 0x100 /* Override existing */
NLM_F_EXCL 0x200 /* Do not touch, if it exists */
NLM_F_CREATE 0x400 /* Create, if it does not exist */