Remove shelling out to mount

Also remove the target from the Mount struct because it should not be
used at all.  The target can be variable and set by a caller, not by the
snapshot drivers.

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

mount.go

@@ -1,8 +1,6 @@
 package containerd
 
 import (
-	"os"
-	"os/exec"
 	"strings"
 	"syscall"
 )
@@ -12,48 +10,23 @@ import (
 type Mount struct {
 	// Type specifies the host-specific of the mount.
 	Type string
-
 	// Source specifies where to mount from. Depending on the host system, this
 	// can be a source path or device.
 	Source string
-
-	// Target is the filesystem mount location.
-	Target string
-
 	// Options contains zero or more fstab-style mount options. Typically,
 	// these are platform specific.
 	Options []string
 }
 
-// MountCommand converts the provided mount into a CLI arguments that can be used to mount the
-func MountCommand(m Mount) []string {
-	return []string{
-		"mount",
-		"-t", strings.ToLower(m.Type),
-		m.Source,
-		m.Target,
-		"-o", strings.Join(m.Options, ","),
-	}
+func (m *Mount) Mount(target string) error {
+	flags, data := parseMountOptions(m.Options)
+	return syscall.Mount(m.Source, target, m.Type, uintptr(flags), data)
 }
 
-func MountAll(mounts ...Mount) error {
-	for _, mount := range mounts {
-		cmd := exec.Command("mount", MountCommand(mount)[1:]...)
-		cmd.Stderr = os.Stderr
-		cmd.Stdout = os.Stdout
-
-		if err := cmd.Run(); err != nil {
-			return err
-		}
-	}
-
-	return nil
-}
-
-func MountFS(mounts []Mount, target string) error {
+// MountAll mounts all the provided mounts to the provided target
+func MountAll(mounts []Mount, target string) error {
 	for _, m := range mounts {
-		flags, data := parseMountOptions(m.Options)
-		if err := syscall.Mount(m.Source, target, m.Type, uintptr(flags), data); err != nil {
+		if err := m.Mount(target); err != nil {
 			return err
 		}
 	}