Apply _netdev mount option in bind mount if available

_netdev mount option is a userspace mount option and
isn't copied over when bind mount is created and remount
also does not copies it over and hence must be explicitly
used with bind mount

pkg/util/mount/mount_test.go

@@ -0,0 +1,60 @@
+/*
+Copyright 2018 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package mount
+
+import (
+	"reflect"
+	"testing"
+)
+
+func TestIsBind(t *testing.T) {
+	tests := []struct {
+		mountOption         []string
+		isBind              bool
+		expectedBindOpts    []string
+		expectedRemountOpts []string
+	}{
+		{
+			[]string{"vers=2", "ro", "_netdev"},
+			false,
+			[]string{},
+			[]string{},
+		},
+		{
+
+			[]string{"bind", "vers=2", "ro", "_netdev"},
+			true,
+			[]string{"bind", "_netdev"},
+			[]string{"bind", "remount", "vers=2", "ro", "_netdev"},
+		},
+	}
+	for _, test := range tests {
+		bind, bindOpts, bindRemountOpts := isBind(test.mountOption)
+		if bind != test.isBind {
+			t.Errorf("Expected bind to be %v but got %v", test.isBind, bind)
+		}
+		if test.isBind {
+			if !reflect.DeepEqual(test.expectedBindOpts, bindOpts) {
+				t.Errorf("Expected bind mount options to be %+v got %+v", test.expectedBindOpts, bindOpts)
+			}
+			if !reflect.DeepEqual(test.expectedRemountOpts, bindRemountOpts) {
+				t.Errorf("Expected remount options to be %+v got %+v", test.expectedRemountOpts, bindRemountOpts)
+			}
+		}
+
+	}
+}