LU-9859 tracefile: convert list_for_each_entry_safe() to while(!list_empty())

LU-9859 tracefile: convert list_for_each_entry_safe() to while(!list_empty())

These loops are removing all elements from a list.
So using while(!list_empty()) makes the intent clearer.

Linux-commit: fdafb01e2c70e6b5321d158a2ff1f20a13d9b365

Change-Id: Idda25888e424a1deaa4d7c6fad427d494b1f56e5
Signed-off-by: NeilBrown <neilb@suse.de>
Reviewed-on: https://review.whamcloud.com/41670
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>