disable dual-mode workaround for RtpIceChannel unless running on Mono

this was already disabled for RTPChannel in d4a2e88

Author: lostmsu

src/net/ICE/RtpIceChannel.cs

@@ -2504,7 +2504,7 @@ protected virtual SocketError SendOverTCP(IceServer iceServer, byte[] buffer)
                     }
 
                     //Prevent Send to IPV4 while socket is IPV6 (Mono Error)
-                    if (dstEndPoint.AddressFamily == AddressFamily.InterNetwork && sendSocket.AddressFamily != dstEndPoint.AddressFamily)
+                    if (isMono && dstEndPoint.AddressFamily == AddressFamily.InterNetwork && sendSocket.AddressFamily != dstEndPoint.AddressFamily)
                     {
                         dstEndPoint = new IPEndPoint(dstEndPoint.Address.MapToIPv6(), dstEndPoint.Port);
                     }

src/net/RTP/RTPChannel.cs

@@ -362,7 +362,7 @@ public enum RTPChannelSocketsEnum
     /// </summary>
     public class RTPChannel : IDisposable
     {
-        private static readonly bool isMono = Type.GetType("Mono.Runtime") != null;
+        internal static readonly bool isMono = Type.GetType("Mono.Runtime") != null;
         private static ILogger logger = Log.Logger;
         protected UdpReceiver m_rtpReceiver;
         private Socket m_controlSocket;