Update grub at the end of mesh install

src/freedombone-image-mesh

             rm /usr/share/images/desktop-base/desktop-background
             ln -s /usr/share/images/desktop-base/${PROJECT_NAME}_mesh_background.png /usr/share/images/desktop-base/desktop-background
         fi
+        if [ -f /etc/default/grub ]; then
+            update-grub
+        fi
         systemctl reboot -i
     fi
 fi