nspawn: Reorder includes to fix compilation

Commit 2e996f4d4b642c5682c608c9692ad2ffae398ab2 added an include
of linux/netlink.h

This kernel header is not self contained in the linux 2.6 kernel
which breaks compilation with an unknown type sa_family_t

A workaround is to include linux/netlink.h after sys/socket.h
man: Fix example to use the new --boot syntax
udev: fix two trivial memleaks in error path

Based-on-a-patch-by: Ian Stakenvicius <axs@gentoo.org>
tmpfiles: Fix memory leak in parse_line()