Set working directory in systemd service file

By default systemd will execute service with root directory
(or home directory for user instance) which might result in
attempts to create files in unexpected place. Let's set it
to 'osmocom' subdir of state directory
(/var/lib for system instance) instead.

Related: OS#4821
Change-Id: Ie8b014e8eac23221a6a7087bb2b886014323680b
diff --git a/contrib/systemd/osmo-smlc.service b/contrib/systemd/osmo-smlc.service
index e159370..ce5a9d3 100644
--- a/contrib/systemd/osmo-smlc.service
+++ b/contrib/systemd/osmo-smlc.service
@@ -4,6 +4,8 @@
 [Service]
 Type=simple
 Restart=always
+StateDirectory=osmocom
+WorkingDirectory=%S/osmocom
 ExecStart=/usr/bin/osmo-smlc -c /etc/osmocom/osmo-smlc.cfg
 RestartSec=2