LU-9679 osc: use rb_entry_safe

LU-9679 osc: use rb_entry_safe

Use rb_entry_safe() instead of container_of() to simplify the code.

Linux-Commit: e3e0293ca9b9 ("staging: lustre: osc: use rb_entry_safe")

Signed-off-by: Geliang Tang <geliangtang@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Mr NeilBrown <neilb@suse.de>
Change-Id: I9f8e19d45d859a6c7b7aa01093a1c2211063874c
Reviewed-on: https://review.whamcloud.com/37604
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Wang Shilong <wshilong@ddn.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>