unit tests: Fixes kubelet util unit tests for Windows

The unit tests are currently failing due to missing imports. This commit
addresses this issue.

Additionally, TestIsUnixDomainSocket expects an error to be raised by
IsUnixDomainSocket if the file does not exist, but on Windows we do not
raise such error.

This issue is addressed by Stat-ing the file, and checking
if the file exists or not. We're also handling the case in which the given
filePath is a named pipe, returning false immediately, instead of trying to
dial it as a Unix domain socket.

pkg/kubelet/util/util_windows.go

@@ -24,6 +24,7 @@ import (
 	"fmt"
 	"net"
 	"net/url"
+	"os"
 	"path/filepath"
 	"strings"
 	"syscall"
@@ -165,6 +166,11 @@ func IsUnixDomainSocket(filePath string) (bool, error) {
 	// does NOT work in 1809 if the socket file is created within a bind mounted directory by a container
 	// and the FSCTL is issued in the host by the kubelet.
 
+	// If the file does not exist, it cannot be a Unix domain socket.
+	if _, err := os.Stat(filePath); os.IsNotExist(err) {
+		return false, fmt.Errorf("File %s not found. Err: %v", filePath, err)
+	}
+
 	klog.V(6).InfoS("Function IsUnixDomainSocket starts", "filePath", filePath)
 	// As detailed in https://github.com/kubernetes/kubernetes/issues/104584 we cannot rely
 	// on the Unix Domain socket working on the very first try, hence the potential need to

pkg/kubelet/util/util_windows_test.go

@@ -22,6 +22,8 @@ package util
 import (
 	"fmt"
 	"math/rand"
+	"net"
+	"os"
 	"reflect"
 	"runtime"
 	"sync"