Call network status callback from UBLOX AT

The helper method call_network_cb, actually does a lot more than calling
the callback. The method has a check that the network status supplied
for the callback is different compared to the internal one. It also sets
the class member if it is changed. This is a bit surprising, given the
name of the method. It also means that it doesn't work in this call, as
the member is already set.

Author: oscarh

features/cellular/framework/targets/UBLOX/AT/UBLOX_AT_CellularContext.cpp

@@ -67,7 +67,7 @@ void UBLOX_AT_CellularContext::do_connect()
     _at.unlock();
 
     if (_status_cb) {
-        call_network_cb(_connect_status);
+        _status_cb(NSAPI_EVENT_CONNECTION_STATUS_CHANGE, _connect_status);
     }
 }