Fix WiFi status on Kindle

WiFi handling is handled asynchronously (deferred to lipc), so this is a
bit clunkier than on devices where we handle WiFi ourselves...

But, basically, try to honor the menu callback when toggling WiFi so
that the status gets updated in the menu.

Fix #4472

frontend/device/kindle/device.lua

@@ -17,27 +17,26 @@ local function kindleEnableWifi(toggle)
 end
 
 local function isWifiUp()
-    -- NOTE: Pilfered from Cervantes, c.f., #4380
-    --       Possibly simpler and more compatible than the lipc approach ;).
-    local file = io.open("/sys/class/net/wlan0/carrier", "rb")
-    if not file then return 0 end
-    local status = tonumber(file:read("*all")) or 0
-    file:close()
-    return status
-
-    --[[
-    local status = 0
+    local status
     local haslipc, lipc = pcall(require, "liblipclua")
     local lipc_handle = nil
     if haslipc and lipc then
         lipc_handle = lipc.init("com.github.koreader.networkmgr")
     end
     if lipc_handle then
-        status = lipc_handle:get_int_property("com.lab126.wifid", "enable")
+        status = lipc_handle:get_int_property("com.lab126.wifid", "enable") or 0
         lipc_handle:close()
+    else
+        -- NOTE: Pilfered from Cervantes, c.f., #4380
+        --       Possibly race-y, if we're extremely unlucky and lipc drops WiFi between our open and our read...
+        --       But then, if we're here, it's because we failed to acquire an lipc handle,
+        --       so it's likely we've failed to do that earlier when trying to toggle WiFi, too...
+        local file = io.open("/sys/class/net/wlan0/carrier", "rb")
+        if not file then return 0 end
+        status = tonumber(file:read("*all")) or 0
+        file:close()
     end
     return status
-    --]]
 end
 
 --[[
@@ -79,12 +78,24 @@ local Kindle = Generic:new{
 }
 
 function Kindle:initNetworkManager(NetworkMgr)
-    NetworkMgr.turnOnWifi = function()
+    function NetworkMgr:turnOnWifi(complete_callback)
         kindleEnableWifi(1)
+        -- NOTE: As we defer the actual work to lipc,
+        --       we have no guarantee the WiFi state will have changed by the time kindleEnableWifi returns,
+        --       so, delay the callback a bit...
+        if complete_callback then
+            local UIManager = require("ui/uimanager")
+            UIManager:scheduleIn(1, complete_callback)
+        end
     end
 
-    NetworkMgr.turnOffWifi = function()
+    function NetworkMgr:turnOffWifi(complete_callback)
         kindleEnableWifi(0)
+        -- NOTE: Same here...
+        if complete_callback then
+            local UIManager = require("ui/uimanager")
+            UIManager:scheduleIn(1, complete_callback)
+        end
     end
 
     NetworkMgr.isWifiOn = function()