device: Don't consider device with only LL address configured

LXC domains are given a veth interface that's up and has a LL address
upon their creation.
device: don't assume connection for veth interfaces

They're supposed to behave as Ethernet. Otherwise the LXC domains won't
be able to use their configured connections with the device.
dhcp-manager: Keep size of PID consistent

Things explode on i386 when marshalling a 32-bit value when a 64-bit one is
expected:

Program received signal SIGSEGV, Segmentation fault.
__memset_sse2 () at ../sysdeps/i386/i686/multiarch/memset-sse2.S:359
359             movdqa  %xmm0, 0x50(%edx)
Missing separate debuginfos, use: debuginfo-install ModemManager-glib-1.5.0-1.fc21.lr3.i686 bluez-libs-5.23-1.fc21.i686 dbus-glib-0.100.2-4.fc21.i686 dbus-libs-1.8.6-3.fc21.i686 freetype-2.5.3-8.fc21.i686 gvfs-1.22.1-2.fc21.i686 libbluray-0.6.2-1.fc21.i686 libgcc-4.9.2-1.fc21.i686 libgudev1-216-11.fc21.i686 libndp-1.4-2.fc21.i686 libnl3-3.2.25-4.fc21.i686 libpng-1.6.10-3.fc21.i686 libsoup-2.48.0-1.fc21.i686 libuuid-2.25.2-1.fc21.i686 libxml2-2.9.1-6.fc21.i686 nss-mdns-0.10-15.fc21.i686 sqlite-3.8.7-1.fc21.i686 systemd-libs-216-11.fc21.i686 teamd-1.14-1.fc21.i686
(gdb) bt
    at /usr/include/bits/string3.h:84
    at ghash.c:481
    at dhcp-manager/nm-dhcp-listener.c:146
Python Exception <class 'gdb.MemoryError'> Cannot access memory at address 0x0:
(gdb)

PIDs use native word width, a gint seems more suitable than gint32 or gint64.
Merge remote-tracking branches 'lr/lr-unmanaged-slaves', 'lr/lr-lxc', 'fd/lr/ipv6-tokens' and 'fd/lr/crashes' into integration