resources: Add stable go-systemd branch for now

We'll update this to point to upstream or JoeJulian once it stops
randomly changing and breaking git master!

.gitmodules

@@ -10,6 +10,6 @@
 [submodule "vendor/gopkg.in/fsnotify.v1"]
 	path = vendor/gopkg.in/fsnotify.v1
 	url = https://gopkg.in/fsnotify.v1
-[submodule "vendor/github.com/joejulian/go-systemd"]
-	path = vendor/github.com/joejulian/go-systemd
-	url = https://github.com/joejulian/go-systemd.git
+[submodule "vendor/github.com/purpleidea/go-systemd"]
+	path = vendor/github.com/purpleidea/go-systemd
+	url = https://github.com/purpleidea/go-systemd

resources/nspawn.go

@@ -29,8 +29,8 @@ import (
 
 	systemdUtil "github.com/coreos/go-systemd/util"
 	"github.com/godbus/dbus"
-	machined "github.com/joejulian/go-systemd/machine1"
 	errwrap "github.com/pkg/errors"
+	machined "github.com/purpleidea/go-systemd/machine1"
 	"github.com/purpleidea/mgmt/global"
 )