Fixed bug where only calibre OPDS catalogs would prompt to enable Wifi.

Tested on Kindle PW3. The error message my device threw was different from what was coded in OPDSBrowser.lua in getCatalog(). Perhaps we should test other devices and see if there are other error messages thrown as well.

frontend/ui/widget/opdsbrowser.lua

@@ -353,7 +353,7 @@ end
 function OPDSBrowser:getCatalog(feed_url)
     local ok, catalog = pcall(self.parseFeed, self, feed_url)
     -- prompt users to turn on Wifi if network is unreachable
-    if not ok and catalog and catalog:find("Network is unreachable") then
+    if not ok and catalog and (catalog:find("Network is unreachable") or catalog:find("host or service not provided")) then
         NetworkMgr:promptWifiOn()
         return
     elseif not ok and catalog then