Use systemctl helper to avoid deadlocks with ynh 2.7 and check path avaibility with no deprecated method

scripts/helpers

@@ -0,0 +1,39 @@
+#!/bin/bash
+
+source /usr/share/yunohost/helpers
+
+#
+# Helper to start/stop/.. a systemd service from a yunohost context,
+# *and* the systemd service itself needs to be able to run yunohost
+# commands.
+# 
+# Hence the need to release the lock during the operation
+#
+# usage : ynh_systemctl yolo restart
+#
+function ynh_systemctl()
+{
+  local ACTION="$1"
+  local SERVICE="$2"
+  local LOCKFILE="/var/run/moulinette_yunohost.lock"
+
+  # Launch the action
+  sudo systemctl "$ACTION" "$SERVICE" &
+  local SYSCTLACTION=$!
+
+  # Save and release the lock...
+  cp $LOCKFILE $LOCKFILE.bkp.$$
+  rm $LOCKFILE
+  
+  # Wait for the end of the action
+  wait $SYSCTLACTION
+
+  # Make sure the lock is released...
+  while [ -f $LOCKFILE ]
+  do
+    sleep 0.1
+  done
+
+  # Restore the old lock
+  mv $LOCKFILE.bkp.$$ $LOCKFILE
+}