update-balena-supervisor: add network-online dependency

There is a race condition present when purging a device and rebooting. If "update-balena-supervisor" comes up before the device can connect to the internet, it will fail to pull the supervisor image. As this service stops "balena-supervisor.service" , this isn't attempted again for at least 15 min = (up to 1 hour) when the "update-balena-supervisor.timer" triggers it.

Change-type: patch
Signed-off-by: Ryan Cooke <ryan@balena.io>

meta-balena-common/recipes-containers/balena-supervisor/balena-supervisor/update-balena-supervisor.service

@@ -19,6 +19,8 @@ Type=simple
 ExecStart=@BASE_BINDIR@/sh @BINDIR@/update-balena-supervisor
 StandardOutput=null
 StandardError=null
+Requires=network-online.target
+After=network-online.target
 
 [Install]
 Alias=update-resin-supervisor.service