Got rid of passthrough properties

We are now building with a version of snapcraft and snapd that doesn't
need the passthrough property for "after" commands in a daemon. We can
get rid of the properties, which will allow us to upload to the snap
store automatically, as a bonus.

Change-Id: I6defdac64f7b61a2894f3d6417597f7d03bc61d4

snapcraft.yaml

@@ -176,8 +176,7 @@ apps:
   ovs-vswitchd:
     command: ovs-wrapper $SNAP/share/openvswitch/scripts/ovs-ctl --no-ovsdb-server --no-monitor --system-id=random start
     stop-command: ovs-wrapper $SNAP/share/openvswitch/scripts/ovs-ctl --no-ovsdb-server stop
-    passthrough:
-      after: [ovsdb-server]
+    after: [ovsdb-server]
     daemon: forking
 #    plugs:
 #      - network
@@ -217,8 +216,7 @@ apps:
   external-bridge:
     command: wait-on-init setup-br-ex
     daemon: oneshot
-    passthrough:
-      after: [ovs-vswitchd]
+    after: [ovs-vswitchd]
 #    plugs:
 #      - network