Fix build on Qt 5.15 Beta 2

Reverts most of 10dae7482c

app/backend/nvcomputer.cpp

@@ -1,5 +1,4 @@
 #include "nvcomputer.h"
-#include "utils.h"
 
 #include <QUdpSocket>
 #include <QHostInfo>
@@ -230,7 +229,7 @@ bool NvComputer::wake()
                     success = true;
                 }
                 else {
-                    qWarning() << "Send failed:" << QSOCK_GET_ERROR(&sock);
+                    qWarning() << "Send failed:" << sock.error();
                 }
             }
         }