gluon-config-mode-geo-location: make altitude show behaviour match docs

Do not show by default, delete old altitude value when a form without
altitude shown is saved.

Fixes #1493

package/gluon-config-mode-geo-location/luasrc/lib/gluon/config-mode/wizard/0400-geo-location.lua

@@ -6,19 +6,13 @@ return function(form, uci)
 
 	local location = uci:get_first("gluon-node-info", "location")
 
-	local function show_altitude()
-		if site.config_mode.geo_location.show_altitude(true) then
-			return true
-		end
-
-		return uci:get_bool("gluon-node-info", location, "altitude")
-	end
+	local show_altitude = site.config_mode.geo_location.show_altitude(false)
 
 	local text = site_i18n._translate("gluon-config-mode:geo-location-help") or pkg_i18n.translate(
 		'If you want the location of your node to ' ..
 		'be displayed on the map, you can enter its coordinates here.'
 	)
-	if show_altitude() then
+	if show_altitude then
 		text = text .. ' ' .. site_i18n.translate("gluon-config-mode:altitude-help")
 	end
 
@@ -30,6 +24,11 @@ return function(form, uci)
 	share_location.default = uci:get_bool("gluon-node-info", location, "share_location")
 	function share_location:write(data)
 		uci:set("gluon-node-info", location, "share_location", data)
+
+		-- The config mode does not have a nicer place to put this at the moment...
+		if not show_altitude then
+			uci:delete("gluon-node-info", location, "altitude")
+		end
 	end
 
 	o = s:option(Value, "latitude", pkg_i18n.translate("Latitude"), pkg_i18n.translatef("e.g. %s", "53.873621"))
@@ -48,7 +47,7 @@ return function(form, uci)
 		uci:set("gluon-node-info", location, "longitude", data)
 	end
 
-	if show_altitude() then
+	if show_altitude then
 		o = s:option(Value, "altitude", site_i18n.translate("gluon-config-mode:altitude-label"), pkg_i18n.translatef("e.g. %s", "11.51"))
 		o.default = uci:get("gluon-node-info", location, "altitude")
 		o:depends(share_location, true)