ensure KMS plugin socket is removed before starting mock in 'encrypt all resources' test

staging/src/k8s.io/apiserver/pkg/storage/value/encrypt/envelope/testing/v1beta1/kms_plugin_mock.go

@@ -69,6 +69,8 @@ func NewBase64Plugin(t *testing.T, socketPath string) *Base64Plugin {
 		socketPath: socketPath,
 	}
 
+	// Make sure we don't have a leftover socket.
+	_ = os.Remove(socketPath)
 	kmsapi.RegisterKeyManagementServiceServer(server, result)
 	if err := result.start(); err != nil {
 		t.Fatalf("failed to start KMS plugin, err: %v", err)