fix(UBNetworkAccessManager): Use atomic_int instead of volatile

volatile is intended for hardware interaction, where changes might
not be obvious from the given code, disabling certain compiler
features.
The intended use is atomic operations, so use that instead.

src/network/UBNetworkAccessManager.h

@@ -30,6 +30,7 @@
 #ifndef UBNETWORKACCESSMANAGER_H
 #define UBNETWORKACCESSMANAGER_H
 
+#include <atomic>
 #include <QtNetwork>
 
 class UBNetworkAccessManager : public QNetworkAccessManager
@@ -50,7 +51,7 @@ class UBNetworkAccessManager : public QNetworkAccessManager
 
         static UBNetworkAccessManager *sNetworkAccessManager;
 
-        volatile int mProxyAuthenticationCount;
+        std::atomic_int mProxyAuthenticationCount;
 
     private slots:
         void authenticationRequired(QNetworkReply *reply, QAuthenticator *auth);