Install systemd services with autotools

Change-Id: I7e4dae6b8c1685e8a673c58a843c41fa0af1b35c
diff --git a/debian/osmo-mgw.install b/debian/osmo-mgw.install
index 39f7c01..ad3d3c6 100644
--- a/debian/osmo-mgw.install
+++ b/debian/osmo-mgw.install
@@ -1,2 +1,3 @@
+lib/systemd/system/osmo-mgw.service
 usr/bin/osmo-mgw
 usr/share/doc/osmo-mgw/examples/osmo-mgw/osmo-mgw.cfg