xfrm_user.c doesn't use netlink correctly

If you read the netlink documentation (and look on how existing users such as rtnetlink or ipt_ULOG uses it), then all messages part of a dump have the NLM_F_MULTI flag set, and the dump is terminated with a NLMSG_DONE message.

The code in net/xfrm/xfrm_user.c however dumps those messages without the NLM_F_MULTI flag. I've hacked a first patch, but apparently it doesn't catch all cases.