configure.ac + debian: Add systemd service file support

Closes: OS#4326
Change-Id: I0d7b6562c1127f005ddbd47298c03942ac3d241d
diff --git a/debian/osmo-remsim-bankd.install b/debian/osmo-remsim-bankd.install
index d8168d5..58de089 100644
--- a/debian/osmo-remsim-bankd.install
+++ b/debian/osmo-remsim-bankd.install
@@ -1 +1,2 @@
 usr/bin/osmo-remsim-bankd
+lib/systemd/system/osmo-remsim-bankd.service