SmtpClientTest Assertion Fail Fix (#76361)

* Eliminate temporary -1 on Socket.Unix.cs

src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.Unix.cs

@@ -8,6 +8,7 @@
 using Microsoft.Win32.SafeHandles;
 using System.Reflection;
 using System.Collections;
+using System.Threading;
 
 namespace System.Net.Sockets
 {
@@ -108,7 +109,7 @@ internal void ReplaceHandleIfNecessaryAfterFailedConnect()
             SocketError errorCode = ReplaceHandle();
             if (errorCode != SocketError.Success)
             {
-                throw new SocketException((int) errorCode);
+                throw new SocketException((int)errorCode);
             }
 
             _handle.LastConnectFailed = false;
@@ -137,14 +138,22 @@ internal SocketError ReplaceHandle()
 
             // Then replace the handle with a new one
             SafeSocketHandle oldHandle = _handle;
-            SocketError errorCode = SocketPal.CreateSocket(_addressFamily, _socketType, _protocolType, out _handle);
+            SocketError errorCode = SocketPal.CreateSocket(_addressFamily, _socketType, _protocolType, out SafeSocketHandle newHandle);
+            Volatile.Write(ref _handle, newHandle);
             oldHandle.TransferTrackedState(_handle);
             oldHandle.Dispose();
+
             if (errorCode != SocketError.Success)
             {
                 return errorCode;
             }
 
+            if (Volatile.Read(ref _disposed) != 0)
+            {
+                _handle.Dispose();
+                throw new ObjectDisposedException(GetType().FullName);
+            }
+
             // And put back the copied settings.  For DualMode, we use the value stored in the _handle
             // rather than querying the socket itself, as on Unix stacks binding a dual-mode socket to
             // an IPv6 address may cause the IPv6Only setting to revert to true.