Fix calculating machine fingerprint.

Start from the fastest NIC (`OrderByDescending` instead of `OrderBy`) and check for length of `>= 12` instead of `> 12`. This results in a better machine identifier on my machine at least.

Author: grokys

src/GitHub.Api/ApiClientConfiguration.cs

@@ -61,10 +61,10 @@ static string GetMachineIdentifier()
             {
                 // adapted from http://stackoverflow.com/a/1561067
                 var fastedValidNetworkInterface = NetworkInterface.GetAllNetworkInterfaces()
-                    .OrderBy(nic => nic.Speed)
+                    .OrderByDescending(nic => nic.Speed)
                     .Where(nic => nic.OperationalStatus == OperationalStatus.Up)
                     .Select(nic => nic.GetPhysicalAddress().ToString())
-                    .FirstOrDefault(address => address.Length > 12);
+                    .FirstOrDefault(address => address.Length >= 12);
 
                 return fastedValidNetworkInterface ?? GetMachineNameSafe();
             }