systemd: depend on networking-online.target

Related: SYS#6400
Change-Id: Ib6c78c76c5f13b9482428ce653a61b03b2aca1d3
diff --git a/contrib/systemd/osmo-mgw.service b/contrib/systemd/osmo-mgw.service
index 13c8515..b187e1a 100644
--- a/contrib/systemd/osmo-mgw.service
+++ b/contrib/systemd/osmo-mgw.service
@@ -1,5 +1,7 @@
 [Unit]
 Description=Osmocom Media Gateway (MGW)
+After=network-online.target
+Wants=network-online.target
 
 [Service]
 Type=simple