osmo-remsim-client: add systemd service script template and etc/default configs

Change-Id: I243f3d8e090d49ca3a1d0a8cf568750b76273c03
diff --git a/contrib/etc_default/osmo-remsim-client b/contrib/etc_default/osmo-remsim-client
new file mode 100644
index 0000000..b1a2187
--- /dev/null
+++ b/contrib/etc_default/osmo-remsim-client
@@ -0,0 +1,4 @@
+# Default settings for osmo-remsim-client This file is sourced by systemd
+
+# Options to pass to osmo-remsim-client
+GLOBAL_CLIENT_OPTS="-s 10.9.99.10 -V 1d50 -P 4004 -C 1"