bump coreos/go-systemd v19, coreos/pkg v4, godbus/dbus v5.0.1

- https://github.com/coreos/go-systemd/compare/v14..v19
  - coreos/go-systemd#248 dbus: add SetPropertiesSubscriber method
  - coreos/go-systemd#251 activation: add support for listeners with names
  - coreos/go-systemd#296 dbus: Fix API break from godbus
- coreos/pkg@v3...v4
  - no changes in vendored code
- https://github.com/godbus/dbus/compare/v3..v5.0.1
  - godbus/dbus#89 introduce MakeVariantWithSignature

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

vendor.conf

@@ -13,9 +13,9 @@ github.com/syndtr/gocapability          d98352740cb2c55f81556b63d4a1ec64c5a319c2
 github.com/vishvananda/netlink          1e2e08e8a2dcdacaae3f14ac44c5cfa31361f270
 
 # systemd integration.
-github.com/coreos/go-systemd            48702e0da86bd25e76cfef347e2adeb434a0d0a6 # v14
-github.com/coreos/pkg                   3ac0863d7acf3bc44daf49afef8919af12f704ef # v3
-github.com/godbus/dbus                  c7fdd8b5cd55e87b4e1f4e372cdb1db61dd6c66f # v3
+github.com/coreos/go-systemd            95778dfbb74eb7e4dbaf43bf7d71809650ef8076 # v19
+github.com/coreos/pkg                   97fdf19511ea361ae1c100dd393cc47f8dcfa1e1 # v4
+github.com/godbus/dbus                  2ff6f7ffd60f0f2410b3105864bdd12c7894f844 # v5.0.1
 github.com/golang/protobuf              18c9bb3261723cd5401db4d0c9fbc5c3b6c70fe8
 
 # Command-line interface.