ScaleIO: Use VolumeHost.GetExec() to execute utilities

This prepares volume plugins to run things in containers instead of running
them on the host.

As consequence, a mount.Exec interface needs to be passed from VolumeHost
down to SioClient.

pkg/volume/scaleio/sio_client.go

@@ -21,7 +21,6 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
-	"os/exec"
 	"path"
 	"path/filepath"
 	"regexp"
@@ -30,6 +29,8 @@ import (
 	"sync"
 	"time"
 
+	"k8s.io/kubernetes/pkg/util/mount"
+
 	sio "github.com/codedellemc/goscaleio"
 	siotypes "github.com/codedellemc/goscaleio/types/v1"
 	"github.com/golang/glog"
@@ -77,13 +78,15 @@ type sioClient struct {
 	inited           bool
 	diskRegex        *regexp.Regexp
 	mtx              sync.Mutex
+	exec             mount.Exec
 }
 
-func newSioClient(gateway, username, password string, sslEnabled bool) (*sioClient, error) {
+func newSioClient(gateway, username, password string, sslEnabled bool, exec mount.Exec) (*sioClient, error) {
 	client := new(sioClient)
 	client.gateway = gateway
 	client.username = username
 	client.password = password
+	client.exec = exec
 	if sslEnabled {
 		client.insecure = false
 		client.certsEnabled = true
@@ -296,7 +299,7 @@ func (c *sioClient) IID() (string, error) {
 
 	if c.instanceID == "" {
 		cmd := c.getSdcCmd()
-		output, err := exec.Command(cmd, "--query_guid").Output()
+		output, err := c.exec.Run(cmd, "--query_guid")
 		if err != nil {
 			glog.Error(log("drv_cfg --query_guid failed: %v", err))
 			return "", err
@@ -355,7 +358,7 @@ func (c *sioClient) Devs() (map[string]string, error) {
 	volumeMap := make(map[string]string)
 
 	// grab the sdc tool output
-	out, err := exec.Command(c.getSdcCmd(), "--query_vols").Output()
+	out, err := c.exec.Run(c.getSdcCmd(), "--query_vols")
 	if err != nil {
 		glog.Error(log("sdc --query_vols failed: %v", err))
 		return nil, err