Single quotes

tests/check-ctrl-alt-del.sh

 
 if [ -f /etc/systemd/system/ctrl-alt-del.target ];then
     ctrl_alt_del=$(ls -l /etc/systemd/system/ctrl-alt-del.target)
-    if [[ "$ctrl_alt_del" !=  *"/dev/null" ]]; then
+    if [[ "$ctrl_alt_del" !=  *'/dev/null' ]]; then
         exit 1
     fi
 else