staging: lustre: fix to use list_for_each_entry_safe() when delete items

Since we will remove items off the list using list_del_init() we need
to use a safe version of the list_for_each_entry() macro aptly named
list_for_each_entry_safe().

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>