Add Exec interface to VolumeHost

This exec should be used by volume plugins to execute mount utilities.
It will eventually execute things in mount containers.

pkg/util/mount/exec.go

@@ -0,0 +1,50 @@
+/*
+Copyright 2017 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 "k8s.io/utils/exec"
+
+func NewOsExec() Exec {
+	return &osExec{}
+}
+
+// Real implementation of Exec interface that uses simple util.Exec
+type osExec struct{}
+
+var _ Exec = &osExec{}
+
+func (e *osExec) Run(cmd string, args ...string) ([]byte, error) {
+	exe := exec.New()
+	return exe.Command(cmd, args...).CombinedOutput()
+}
+
+func NewFakeExec(run runHook) *FakeExec {
+	return &FakeExec{runHook: run}
+}
+
+// Fake for testing.
+type FakeExec struct {
+	runHook runHook
+}
+type runHook func(cmd string, args ...string) ([]byte, error)
+
+func (f *FakeExec) Run(cmd string, args ...string) ([]byte, error) {
+	if f.runHook != nil {
+		return f.runHook(cmd, args...)
+	}
+	return nil, nil
+}