[Debuggability/Serviceability] Add logging for important workflows

[pdhamdhere]

We do not log error in Plugin for "Get" request;

	status, err := d.GetVolume(r.Name)
	if err != nil {                              <<<<<No logging
		return volume.Response{Err: err.Error()}
	}

func (d *VolumeDriver) GetVolume(name string) (map[string]interface{}, error) {
	return d.ops.Get(name)
}

func (v VmdkOps) Get(name string) (map[string]interface{}, error) {
	log.Debugf("vmdkOps.Get name=%s", name)
	str, err := v.Cmd.Run("get", name, make(map[string]string))
	if err != nil {            <<<<< No logging
		return nil, err
	}