Reset the SocketAsyncEventArgs.in_progress flag after failure

When a DNS error occurs the flag needs to be reset before the Args
object is put back in the queue for reuse. Failure to do so causes an
"Operation already in progress" exception on a future request.

Fixes Bee.Stevedore.Program.Tests.StevedoreTelemetryTests.SendOutbox_GoodServer_EventsSentInSingleBatch
in Unity

Author: bholmes

mcs/class/referencesource/System/net/System/Net/Sockets/Socket.cs

@@ -7782,7 +7782,16 @@ public bool ConnectAsync(SocketAsyncEventArgs e) {
                 e.StartOperationCommon(this);
                 e.StartOperationWrapperConnect(multipleConnectAsync);
 
-                retval = multipleConnectAsync.StartConnectAsync(e, dnsEP);
+                try
+                {
+                    retval = multipleConnectAsync.StartConnectAsync(e, dnsEP);
+                }
+                catch
+                {
+                    // Clear in-use flag on event args object.
+                    Interlocked.Exchange(ref e.in_progress, 0);
+                    throw;
+                }
             } 
             else {
                 // Throw if remote address family doesn't match socket.
@@ -7880,7 +7889,16 @@ public static bool ConnectAsync(SocketType socketType, ProtocolType protocolType
                 e.StartOperationCommon(attemptSocket);
                 e.StartOperationWrapperConnect(multipleConnectAsync);
 
-                retval = multipleConnectAsync.StartConnectAsync(e, dnsEP);
+                try
+                {
+                    retval = multipleConnectAsync.StartConnectAsync(e, dnsEP);
+                }
+                catch
+                {
+                    // Clear in-use flag on event args object.
+                    Interlocked.Exchange(ref e.in_progress, 0);
+                    throw;
+                }
             } else {
                 Socket attemptSocket = new Socket(endPointSnapshot.AddressFamily, socketType, protocolType);
                 retval = attemptSocket.ConnectAsync(e);