devicemapper: Create a method to get device info with deferred remove field

Deferred reove functionality was added to library later. So in old version
of library it did not report deferred_remove field. 

Create a new function which also gets deferred_remove field and it will be
called only on newer version of library. 

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>

devicemapper/devmapper.go

@@ -87,16 +87,17 @@ type (
 		Device []uint64
 	}
 	Info struct {
-		Exists        int
-		Suspended     int
-		LiveTable     int
-		InactiveTable int
-		OpenCount     int32
-		EventNr       uint32
-		Major         uint32
-		Minor         uint32
-		ReadOnly      int
-		TargetCount   int32
+		Exists         int
+		Suspended      int
+		LiveTable      int
+		InactiveTable  int
+		OpenCount      int32
+		EventNr        uint32
+		Major          uint32
+		Minor          uint32
+		ReadOnly       int
+		TargetCount    int32
+		DeferredRemove int
 	}
 	TaskType    int
 	AddNodeType int
@@ -222,6 +223,14 @@ func (t *Task) GetInfo() (*Info, error) {
 	return info, nil
 }
 
+func (t *Task) GetInfoWithDeferred() (*Info, error) {
+	info := &Info{}
+	if res := DmTaskGetInfoWithDeferred(t.unmanaged, info); res != 1 {
+		return nil, ErrTaskGetInfo
+	}
+	return info, nil
+}
+
 func (t *Task) GetDriverVersion() (string, error) {
 	res := DmTaskGetDriverVersion(t.unmanaged)
 	if res == "" {
@@ -531,6 +540,17 @@ func GetInfo(name string) (*Info, error) {
 	return task.GetInfo()
 }
 
+func GetInfoWithDeferred(name string) (*Info, error) {
+	task, err := TaskCreateNamed(DeviceInfo, name)
+	if task == nil {
+		return nil, err
+	}
+	if err := task.Run(); err != nil {
+		return nil, err
+	}
+	return task.GetInfoWithDeferred()
+}
+
 func GetDriverVersion() (string, error) {
 	task := TaskCreate(DeviceVersion)
 	if task == nil {