Adds retry support to Windows AnonDialer

Adds retry support to AnonDialer if the pipe does not exist. This will
retry up to the timeout for the pipe to exist and connect. This solves
the race between the containerd-shim-* start command and the
reinvocation.

Signed-off-by: Justin Terry (VM) <juterry@microsoft.com>

runtime/v2/shim/util_windows.go

@@ -20,6 +20,7 @@ import (
 	"context"
 	"fmt"
 	"net"
+	"os"
 	"syscall"
 	"time"
 
@@ -48,7 +49,25 @@ func SocketAddress(ctx context.Context, id string) (string, error) {
 
 // AnonDialer returns a dialer for a npipe
 func AnonDialer(address string, timeout time.Duration) (net.Conn, error) {
-	return winio.DialPipe(address, &timeout)
+	var c net.Conn
+	var lastError error
+	start := time.Now()
+	for {
+		remaining := timeout - time.Now().Sub(start)
+		if remaining <= 0 {
+			lastError = errors.Errorf("timed out waiting for npipe %s", address)
+			break
+		}
+		c, lastError = winio.DialPipe(address, &remaining)
+		if lastError == nil {
+			break
+		}
+		if !os.IsNotExist(lastError) {
+			break
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	return c, lastError
 }
 
 // NewSocket returns a new npipe listener