Fix blue lockscreen in GNOME (varietywalls#302)

Previous to this commit when a wallpaper was changed,
under GNOME and Fedora the lockscreen wallpaper would
default to a solid blue.

Also moved the code for the lockscreen change right under
the GNOME section in `set_wallpaper` and make sure the
picture-option for the screen saver is set to 'zoom'.

data/scripts/set_wallpaper

@@ -175,6 +175,13 @@ if [ "$(gsettings get org.gnome.desktop.screensaver picture-options)" == "'none'
   gsettings set org.gnome.desktop.screensaver picture-options 'zoom'
 fi
 
+# GNOME Screensaver / Lock screen - thanks to George C. de Araujo for the patch
+gsettings set org.gnome.desktop.screensaver picture-uri "file://$WP" 2> /dev/null
+if [ "$(gsettings get org.gnome.desktop.screensaver picture-options)" == "'none'" ]; then
+    gsettings set org.gnome.desktop.screensaver picture-options 'zoom'
+fi
+
+
 # Deepin
 if [ "$(gsettings list-schemas | grep -c com.deepin.wrap.gnome.desktop.background)" -ge 1 ]; then
   gsettings set com.deepin.wrap.gnome.desktop.background picture-uri "file://$WP"