If we call
setConfiguration(QNetworkConfiguration());
This sets an invalid configuration on the QNAM.
But later, when we really go online because interfaces are discovered,
QNetworkAccessManagerPrivate::_q_onlineStateChanged is called (with isOnline=true).
And this will set the state to disconnected because customNetworkConfiguration is
true, and the networkConfiguration state is disabled.
The workaround we to fix another bug on Windows in which the default network
configuration was not behaving properly.
The issue on linux is hard to reproduce and only happen in some condition,
but it was reproduced on smashbox when they run two owncloudcmd at the same time.
Issues: #4720 , #3600
The proxyAuthenticationRequired() signal now goes to the
ProxyAuthHandler class. That class will try to read the proxy settings
from the keychain or ask the user about them.
We won't ask the user for credentials for explicitly configured proxies.
It also does not change how the credentials for explicitly configured
proxies are stored. (see #261)
