core: make veth devices default-unmanaged for now

We only want to treat a veth device as ethernet if (a) NM is running
inside a container, and (b) the veth in question is the "inside" end
of the veth, not the outside. Unfortunately, we don't have good
heuristics for this at the moment, so just ignore veths for now.

https://bugzilla.gnome.org/show_bug.cgi?id=731014
(cherry picked from commit ebeaeaed4d)

src/devices/nm-device-veth.c

@@ -111,6 +111,7 @@ nm_device_veth_new (NMPlatformLink *platform_device)
 static void
 nm_device_veth_init (NMDeviceVeth *self)
 {
+	nm_device_set_initial_unmanaged_flag (NM_DEVICE (self), NM_UNMANAGED_DEFAULT, TRUE);
 }
 
 static void