Re-add [desktop] item in pcmanfm.conf, to correctly load settings on first start (LP: #1551446)

src/etc/xdg/pcmanfm/lubuntu/pcmanfm.conf

@@ -7,6 +7,21 @@ mount_on_startup=1
 mount_removable=1
 autorun=1
 
+[desktop]
+wallpaper_mode=center
+wallpaper_common=1
+wallpapers_configured=1
+wallpaper0=/usr/share/lubuntu/wallpapers/lubuntu-default-wallpaper.png
+wallpaper=/usr/share/lubuntu/wallpapers/lubuntu-default-wallpaper.png
+desktop_bg=#2e4060
+desktop_fg=#ffffff
+desktop_shadow=#000000
+desktop_font=Ubuntu 11
+sort=mtime;ascending;
+show_documents=0
+show_trash=1
+show_mounts=1
+
 [ui]
 always_show_tabs=0
 max_tab_chars=32