QNetworkSettingsWireless::supportsSecurity doesn't report correct Wifi security protocol

The supported security protocols of a Wifi service reported by QNetworkSettingsWireless::supportsSecurity are not reliable. They change randomly in environments with a lot of Wifi services. 

Root cause:

1. The security protocols of an Wifi service are saved in the class QNetworkSettingsWireless in the member variable m_securityFlags
2. They are saved assigned by bitwise OR in QNetworkSettingsWireless::setSecurity
3. The problem is that the m_securityFlags variable is not initialized in the constructor and therefore when checked via bitwise OR return unpredictable values. 

Fix:

Initialize m_securityFlags to 0 in the constructor of QNetworkSettingsWireless

In addition the other member variables of QNetworkSettingsWireless should be also initialized, e.g. m_hidden=false, m_signalStrength=0, m_isOutOfRange=false