QAuthenticator: Reprioritize authentication methods

The addition of Negotiate to QAuthenticator caused a soft sort of
regression in environments where there is key distribution center
set up. This was due to how QAuthenticator works in that it will
simply prefer the latest entry in the enum, which now was Negotiate,
which sadly wasn't really a valid option in that situation. And it is
not smart enough to fall back and try another method.

To work around this issue we re-order the enum to prioritize
authentication methods to restore previous behavior.
Note that Negotiate is still preferred over Basic and None because
they're not likely to appear together.

Pick-to: 5.15
Task-number: QTBUG-83905
Change-Id: Ic528318b6b711aa04d42a86c684452bb6ebde112
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

src/network/kernel/qauthenticator_p.h

@@ -71,7 +71,7 @@ class QGssApiHandles;
 class Q_AUTOTEST_EXPORT QAuthenticatorPrivate
 {
 public:
-    enum Method { None, Basic, Ntlm, DigestMd5, Negotiate };
+    enum Method { None, Basic, Negotiate, Ntlm, DigestMd5, };
     QAuthenticatorPrivate();
     ~QAuthenticatorPrivate();