refs #857, check if network is accessible in readers

* new read state "skipped"
* renamed to "isNetworkConnectedAndAccessible"
* checking before reading, which would only fail if network is not accessible

src/blackcore/vatsim/vatsimbookingreader.cpp

@@ -67,7 +67,7 @@ namespace BlackCore
 
         void CVatsimBookingReader::ps_read()
         {
-            if (!this->isNetworkAvailable())
+            if (!this->isNetworkConnectedAndAccessible())
             {
                 CLogMessage(this).warning("No network, cannot read VATSIM bookings");
                 return;