Call temp mounts and unmount in containerd server

Fixes #2004

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

mount/temp_unix.go

@@ -0,0 +1,47 @@
+// +build !windows
+
+package mount
+
+import (
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+)
+
+// SetTempMountLocation sets the temporary mount location
+func SetTempMountLocation(root string) error {
+	root, err := filepath.Abs(root)
+	if err != nil {
+		return err
+	}
+	if err := os.MkdirAll(root, 0700); err != nil {
+		return err
+	}
+	tempMountLocation = root
+	return nil
+}
+
+// CleanupTempMounts all temp mounts and remove the directories
+func CleanupTempMounts(flags int) error {
+	mounts, err := Self()
+	if err != nil {
+		return err
+	}
+	var toUnmount []string
+	for _, m := range mounts {
+		if strings.HasPrefix(m.Mountpoint, tempMountLocation) {
+			toUnmount = append(toUnmount, m.Mountpoint)
+		}
+	}
+	sort.Sort(sort.Reverse(sort.StringSlice(toUnmount)))
+	for _, path := range toUnmount {
+		if err := UnmountAll(path, flags); err != nil {
+			return err
+		}
+		if err := os.Remove(path); err != nil {
+			return err
+		}
+	}
+	return nil
+}