MSC: use systemd dropin override

Use override file instead of writing the unit service file directly.

modules/rhizo_base/files/systemd/osmo-msc.override

@@ -0,0 +1,3 @@
+[Service]
+ExecStart=
+ExecStart=/usr/bin/osmo-msc -c /etc/osmocom/osmo-msc.cfg -l /var/lib/osmocom/sms.db

modules/rhizo_base/manifests/osmocom.pp

@@ -9,6 +9,7 @@
 
 class rhizo_base::osmocom {
 
+  include systemd
   $network_name    = $rhizo_base::network_name
   $mcc             = $rhizo_base::mcc
   $mnc             = $rhizo_base::mnc
@@ -131,10 +132,10 @@ class rhizo_base::osmocom {
       require => Package['osmo-sip-connector'],
     }
 
-  file { '/lib/systemd/system/osmo-msc.service':
-      ensure   => present,
-      source   => 'puppet:///modules/rhizo_base/systemd/osmo-msc.service',
-    }
+  systemd::dropin_file { 'override.conf':
+      unit    => 'osmo-msc.service',
+      source  => 'puppet:///modules/rhizo_base/systemd/osmo-msc.override'
+  }
 
   file { '/lib/systemd/system/osmo-mgw-msc.service':
       ensure   => present,