Add vpnclient checker timer and upgrade backups, to enable Bram to sleep better

conf/ynh-vpnclient-checker.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+if ! ip link show tun0 &> /dev/null; then
+  systemctl restart ynh-vpnclient &> /dev/null
+fi
+
+exit 0